Stellar blue IQOS 3 DUO holder and charger in businessman's hand with HEETS stick inserted

The science and vision behind IQOS.

IQOS is the combination of science, technology and vision.

PMI building in Switzerland

Science behind heated tobacco

We believe in science. We believe it can change the lives of millions of smokers, who would otherwise continue to smoke. To this effect, we recruited scientists to work on an important idea: developing less harmful products that cigarette smokers can switch to if they don’t quit. Hundreds of scientists and engineers at PMI’s global Research and Development centers in Switzerland and Singapore have developed and evaluated IQOS, an innovative electronic device that heats and not burns tobacco. It produces a tobacco vapour that delivers tobacco taste and nicotine. 

Tested to the highest standards.

IQOS has gone through robust scientific assessments, including, to date, 18 non-clinical and 10 clinical studies involving thousands of participants.  The totality of evidence available shows that, while IQOS use is not risk-free, switching completely to IQOS presents less risk to your health than continuing to smoke cigarettes*. 

Do you want to find out why we can conclude this? Learn more about some of the key pieces of scientific evidence on IQOS.

Important information: IQOS is not risk-free. It contains nicotine, which is addictive.

*Source: Based on overall evidence available from comparing IQOS and continuing smoking.

Brilliant gold IQOS 3 DUO holder with HEETS stick and charger in hand

Why heating is better.

Technology – the world revolves around it. Over the years, it has radically changed our lives for the better. The way we work, the way we communicate, the way we travel. By combining science and technology is how we developed a better alternative to continued smoking.

IQOS is changing for the better the way adult smokers, who would otherwise continue to smoke, can enjoy tobacco.

IQOS heats tobacco instead of burning it for a simple reason: the burning of tobacco emits high amounts of harmful chemicals like carbon monoxide. IQOS HeatControl™ Technology prevents tobacco from burning, which means it significantly reduces the number and level of harmful chemicals emitted compared to cigarette smoke.*

Important information: IQOS is not risk free, it delivers nicotine which is addictive. 

 * Average reductions in levels of a range of harmful chemicals (excluding nicotine) compared to cigarette smoke. 

IQOS DUO holder heats up to 350°C

Heating technology.

When you light a cigarette, the high temperature creates smoke, a burned taste and many harmful substances. Tobacco is burned in this process. Cigarette smoke is a complex mixture of over 6 000 chemical substances, around 100 of which have been linked to smoking-related diseases by public health authorities. Unlike cigarettes, IQOS heats tobacco at a much lower temperature using the unique HeatControl technology. This releases the aroma and flavor of real tobacco with nicotine, without burning. IQOS produce no smoke and generates 95% less harmful chemicals compared to cigarettes.*

IMPORTANT INFORMATION: It does not necessarily equal a 95% reduction in risk. IQOS is not risk-free. 

* “95% less” represents the average reductions in levels of a range of harmful chemicals (excluding nicotine) compared to the smoke of a reference cigarette (3R4F). See Important Information on

IQOS DUO holder heats up to 350°C
Cigarette filter with brown combustion stains compared to IQOS HEETS stick in IQOS 3 DUO holder with no equivalent stain

Cigarettes produce tar, IQOS doesn’t

“Tar” is the residue from smoke after a cigarette has burned. IQOS does not produce tar because it heats tobacco instead of burning it. It generates an aerosol residue that is fundamentally different from “Tar” and consists of significantly lower levels of harmful chemicals.* Switching completely to IQOS is less harmful than continuing to smoke.**

IMPORTANT INFORMATION: Although IQOS does not produce tar, IQOS is not risk free, and delivers nicotine which is addictive. 

*Average reductions in the levels of a range of harmful chemicals (excluding nicotine) compared to cigarette smoke.

** Source: Based on the totality of evidence available for IQOS in comparison with continuing to smoke.

Frequently asked questions

IQOS is an electronic device that heats a solid tobacco stick similar to a cigarette. IQOS produces aerosol, as opposed to smoke. Compared to smoke from the reference cigarette created for research purposes, the aerosol contains 95% less harmful substances on average.

IQOS heats tobacco, as opposed to burning it. As a result, IQOS produces neither cigarette smoke nor tar. It only releases water vapor, referred to as aerosol, which contains less harmful and less potentially harmful compounds (HPHCs) than cigarette smoke. The aerosol consists of tiny droplets that rapidly evaporate without remaining in the air.

Laboratory analyses performed by Philip Morris International show that the aerosol produced by IQOS devices contains significantly lower concentrations of harmful and potentially harmful compounds than cigarette smoke. On average, the quantity of HPHCs in aerosol produced by IQOS (with the exception of nicotine) is as much as 95% lower compared to HPHC content in smoke produced by the 3R4F reference cigarette. The lower values have been demonstrated to exist per single tobacco stick and per milligram of nicotine. An important finding is that the observed nicotine concentrations are not significantly lower compared to cigarettes. Thanks to that, IQOS is an acceptable alternative to cigarettes for adult smokers.


Cigarette smoke is a mixture of the air and dispersed particulate matter produced by burning organic matter, in this case tobacco. In contrast, IQOS tobacco-heating devices cause the evaporation of a mixture of water, nicotine, and glycerin. Cigarette smoke therefore contains solid particulate matter produced by burning, unlike the aerosol released by IQOS, which contains liquid particles. 
Cigarette smoke contains larger solid particles that are inhaled by both smokers and bystanders. These substances then stay in the human body. Likewise, they accumulate on surrounding surfaces and remain in the environment, where they are the main source of the pungent odor associated with cigarettes.

Observations using electron microscopy have confirmed that the aerosol produced by IQOS contains no measurable particulate matter.

Aerosol from tobacco sticks for IQOS devices only comprises tiny droplets, which rapidly evaporate or are absorbed, depending on the surrounding environment.





Water and glycerin account for 50% of the volume of smoke

Water and glycerin account for 90% of the volume of aerosol

Harmful substances

Harmful substances reduced by 95%

Contains solid particles of carbon compounds

No solid particles of carbon compounds



IQOS delivers nearly the same amount of nicotine as conventional cigarettes. A survey mapping user comportment detected a high degree of willingness to use an IQOS device instead of cigarettes. The ascertained user satisfaction with the product suggests that IQOS can be an alternative capable of providing adult smokers with a full-fledged substitute for cigarettes. The best choice, however, is to quit using tobacco and nicotine altogether.

Using IQOS delivers a nearly identical amount of nicotine as cigarettes, but the user's exposure to harmful substances is significantly lower from tobacco heating devices – it is comparable to the control group of abstaining smokers. For additional information, visit the Health section. Studies involving IQOS users have found that the level of nicotine and the time distribution of its maximum concentration in blood are comparable to those detected in smokers of conventional cigarettes. Likewise, the urge to smoke appeared at a similar frequency in both groups. The findings suggest that adult smokers who switch from cigarettes to IQOS do not feel the need to use their IQOS device more often than conventional cigarettes and that they consider IQOS a satisfactory alternative. Additional information is available here.

This conclusion is corroborated by the outcome of whole offer tests (WOT) performed prior to the placement of the product on the market. The tests showed that a large number of the participating adult smokers began using IQOS in the first week of the study, either exclusively (> 95% of all consumed tobacco products) or mostly (≥ 70% of all consumed tobacco products). These tests involving volunteer subjects were conducted in five countries: Germany, Italy, Japan, Switzerland, and South Korea. 

The outcome of surveys also consistently shows that IQOS is generally unattractive to adult non-smokers, as evidenced by low interest in using IQOS among respondents from the ranks of adult abstaining smokers and lifelong adult non-smokers. In this regard, interest in using IQOS is comparably as low as interest in smoking cigarettes. The results obtained in the cohort of young underage non-smokers are comparable to data collected in the group of their adult counterparts. These findings are nearly identical to the results of studies conducted after the product was introduced on the market, which detected only a negligible rise in the number of users who began smoking or started again after previously quitting. The conclusion can therefore be drawn that IQOS is not found attractive by teenaged non-smokers.

Additional information is available here and here.

For adult smokers to be willing to switch to products carrying reduced health risks, such products must represent a comparable, satisfactory alternative. Nicotine plays an important role in this regard. Numerous independent studies have confirmed that even though using nicotine is not without risks, nicotine is not the primary cause of smoking-related diseases. Most of the harmful substances are caused by burning. A dramatic reduction of harmful substances can be achieved by eliminating burning, which is the purpose of developing reduced-risk products. Hence, the goal of Philip Morris International is to provide products delivering comparable flavor, ritual, and nicotine content to adult smokers to facilitate as much as possible switching to the reduced-risk alternatives of tobacco use.
Nicotine is a plant-derived compound naturally contained in tobacco. It has stimulating and relaxing effects. However, it is an addictive substance, to which users become addicted and which affects the nervous system. Using nicotine is therefore not without risks. According to the International Agency for Research on Cancer (IARC), nicotine is neither classified as carcinogenic, nor is it the primary cause of smoking-related diseases. However, the same does not apply to the several thousand other toxic compounds produced by tobacco burning in conventional cigarettes. Nicotine in any form should be avoided by risk groups. Details are described in the Environment section. Information on nicotine content is normally stated on cigarette packs. It is measured using a testing procedure established by the International Organization for Standardization (ISO). All variants of HEETS tobacco sticks have been measured to contain 0.5 mg of nicotine under constant testing conditions. However, the testing procedure has been designed for cigarettes. Using it for testing the nicotine content in HEETS tobacco sticks is inexact and may yield inconsistent and inaccurate results. In addition, nicotine intake from IQOS use is affected by the comportment of specific users.

Tobacco tar is produced by the burning of organic matter. Tar is only produced by conventional cigarettes. IQOS and electronic cigarettes do not produce tar, because these devices do not burn tobacco. Tar is a dark oily liquid containing mostly toxic, carcinogenic substances. Information on tar content in tobacco products may be misleading, because the level of tar in no way reflects its composition and potential harmfulness. For that reason, the EU Tobacco Products Directive introduced in 2014 states that information on the content of tar, nicotine, and carbon monoxide on cigarette packs is misleading and liable to suggest that certain cigarettes are less harmful than others. It was one of the reasons why governments and health organizations have supported the removal of this information from cigarette packaging.
From time to time, the remains of tobacco from tobacco sticks may be found in your IQOS device. However, such residues are dried pieces of reconstituted tobacco that has lost some of its humidity by being heated, for which reason the tobacco’s color has changed as well. It remains tobacco, not tar.


Using IQOS delivers a nearly identical amount of nicotine as cigarettes, but the user's exposure to harmful substances is significantly lower from tobacco heating devices – exposure is comparable to the quantity of harmful substances detected in the control group of abstaining smokers. Studies involving IQOS users have found that the level of nicotine and the time distribution of its maximum concentration in blood are comparable to the values detected in the smokers of conventional cigarettes. 
Yes. A person can overdose on nicotine as is the case with many other substances. A condition in which the human body is unable to clear out nicotine can cause mood swings, insomnia, nausea, headache, perspiration, and an accelerated heart rate. In such a case, the optimal solution is stopping using tobacco products, at least temporarily. Overdosing on nicotine is not life threatening – it is impossible to reach or even come close to life-threatening levels of nicotine by smoking. A life-threatening level is estimated to amount to approximately 500-1,000 mg of nicotine per adult ingested in its entirety.
No, IQOS is not a product intended to help smokers quit smoking. It is a device designed to be a reduced-risk alternative to conventional cigarettes for adult smokers who do not want, and do not plan, to stop smoking.
Laboratory analyses performed by Philip Morris International show that aerosol produced by IQOS devices contains significantly lower concentrations of harmful and potentially harmful compounds than cigarette smoke. On average, the values were as much as 95% lower compared to the 3R4F reference cigarette.
Yes, IQOS has been designed as a full-fledged alternative for adult smokers who would otherwise continue smoking conventional cigarettes. IQOS is not without risks, but it represents the best choice for this group of users in regard to nicotine intake and reduction of harmful substances. To fully avoid risks associated with smoking, people should refrain from starting smoking in the first place. 
IQOS 3 DUO holder inside the charger

Tobacco vapour vs smoke.

IQOS tobacco vapour is less harmful than cigarette smoke. To demonstrate this, we conducted a comprehensive assessment programme that included 10 clinical studies on aerosol chemistry (as well as data from 18 non-clinical studies), and involved thousands of participants in the US, Japan, UK and Poland. Evidence demonstrates that switching completely to IQOS, while not risk-free, presents less risk of harm compared with continuing to smoke cigarettes*.

Important information: IQOS is not risk-free. It contains nicotine, which is addictive.

*Source: Based on overall evidence available from comparing IQOS and continuing smoking.

Lit cigarette end compared to IQOS HEETS stick in IQOS 3 DUO holder.

IQOS emits less harmful chemicals than cigarettes

Cigarettes burn tobacco, which produces high amounts of carbon monoxide. IQOS doesn’t burn tobacco, producing on average 98% less carbon monoxide (CO) and significantly lower levels of other harmful chemicals compared to cigarettes.*

IMPORTANT INFORMATION: This does not mean a 98% reduction in risk. IQOS is not risk-free, and delivers nicotine which is addictive.

*Source: We measured the levels of certain harmful chemicals prioritised for reporting by renowned public health organisations, and these are reduced on average by 95% compared to the smoke of a cigarette (nicotine excluded).

Indoor air quality.

Indoor Air Quality (“IAQ”) refers to the air quality inside buildings, generally based on the principle of ensuring the health and comfort of the occupants.  Temperature, humidity and contaminants are some of the factors that can affect the indoor air quality. But, human presence and activities such as cooking, cleaning or smoking have been proven to have considerable impact. 

To enhance our knowledge and understanding the impact of IQOS on indoor air quality we conducted studies simulating “real-world” conditions in an environmentally controlled room. Our testing methods are validated, and ISO accredited.

Our study shows that, because IQOS does not burn tobacco and it does not generate smoke and it drastically reduces levels of harmful chemicals like carbon monoxide, it does not negatively impact indoor air quality. This means that the few compounds we nevertheless detected were found at very low concentrations and far below the maximum exposure levels defined in existing air quality guidelines.

Illustration contrasting effects of cigarette smoke versus IQOS on indoor air quality.

Frequently asked questions

IQOS produces aerosol that mostly consists of tiny water droplets that evaporate in the indoor environment within several minutes.

Studies have been conducted by Philip Morris International and independent scientists to monitor the time needed for the aerosol from IQOS devices and cigarette smoke to dissipate in an indoor setting. The study measured the concentration of particulate matter in the air before and after the use of tobacco products. After using one tobacco stick in an IQOS device, the concentration of aerosol and particles in the room returned to normal within one minute, while the dissipation of smoke from a single cigarette lasted as long as three hours and 45 minutes.

The most recent study conducted by Philip Morris International shows that the bodies of non-smokers exposed to aerosol from IQOS devices contain no traces of nicotine or harmful compounds produced by smoke from conventional cigarettes.

To analyze effects similar to passive smoking, over 300 adult volunteers were on two occasions invited for a monitored dinner, during which tests were performed. During the first dinner, all participants were prohibited from using any tobacco products, and samples of their blood and urine were taken to determine the baseline values. During the subsequent dinner, IQOS tobacco sticks were used, and once again, blood and urine samples were taken from all of the subjects. The results showed that the bodies of the non-smokers present contained no measurable traces of nicotine or tobacco nitrosamines. (Nitrosamines are released into the environment by smoking conventional cigarettes and are regarded as some of the most important carcinogens contained in cigarette smoke.) The conclusions were drawn based on a chemical analysis of blood and urine samples taken from all of the participants before and after the dinner. 
The entire study and the relevant data are being prepared for publication in specialized scientific magazines.


IQOS is a better choice than smoking conventional cigarettes, but it is not without risks. IQOS does not have a detrimental impact on indoor air quality that would exceed legal limits, despite the fact that it leaves minimal traces of nicotine and acetaldehyde in the air. For this reason, IQOS needs to be used considerately and with moderation, particularly in the proximity of risk groups. Likewise, IQOS must be used in compliance with applicable laws and regulations.
The risk groups that should avoid using IQOS and the aerosol it produces mainly include teenagers, pregnant and lactating women, and people suffering from diabetes and cardiovascular diseases. In addition, some users may experience an allergic reaction to some of the substances of the aerosol from IQOS devices during indoor use.

When tobacco is heated in an IQOS device, the genuine tobacco aroma is released, and it can be smelled by people around you.

Some people find the odor produced by IQOS aerosol unpleasant. It is because the aroma of tobacco is very specific, and not everyone finds it enjoyable. In contrast, other people find the odor pleasant. The important factor that must be kept in mind is that unlike conventional cigarettes, IQOS does not have a detrimental effect on indoor air quality.

The results of research have confirmed that IQOS does not have a detrimental effect on the quality of air in enclosed spaces. Aerosol released into the environment during use contains nicotine, acetaldehyde, and glycerin, however in values that are below the limits laid down in EU and WHO air quality directives. All testing methods were validated and certified according to ISO standards.

Because IQOS devices heat tobacco instead of burning it, they are not a source of any smoke and do not produce sidestream smoke either.

Sidestream smoke is the main constituent of tobacco smoke in the environment. Sidestream smoke mainly consists of smoke coming from the lighted end of a burning or smoldering cigarette. However, IQOS produces no such sidestream smoke, because IQOS devices only release aerosol after puffing. Water vapor amounts to nearly 80% of the aerosol. Using IQOS in an enclosed space therefore has no detrimental effect on indoor air quality.

The most recent study conducted by Philip Morris International shows that the bodies of non-smokers exposed to aerosol from IQOS devices don’t have any measured traces of nicotine or the harmful compounds produced by the smoke from conventional cigarettes in their bodies. The fact is that IQOS produces no smoke, unlike burning tobacco in cigarettes. Consequently, IQOS is not a source of any smoke dissipated in the surrounding air and therefore not a source of passive smoke.
Tobacco sticks contain nicotine that is released into the surrounding environment during use. Even though nicotine is a natural compound found in tobacco that is not classified as carcinogenic, it is not suitable for children and risk groups. Nicotine has stimulating and relaxing effects, but it is addictive and affects the body, particularly the development of the nervous system.
Nicotine has stimulating and relaxing effects, but it is addictive and affects the body, particularly the development of the nervous system. Like young persons, pregnant women should completely refrain from exposing themselves to nicotine in any form, and they should completely avoid the inhalation of cigarette smoke. Philip Morris International strongly recommends against using IQOS during pregnancy and lactation.
Yes, at your own discretion. Even though IQOS is a better choice than smoking conventional cigarettes, it is not without risk. IQOS does not have a negative impact on indoor air quality that would exceed legal limits, but it leaves traces of nicotine and acetaldehyde in the air. For this reason, IQOS needs to be used considerately and moderately, particularly in the proximity of risk groups.
IQOS is an electronic device containing numerous fine components and materials. IQOS 2.4 Plus, functions correctly within the temperature range of 10 to 40 °C. IQOS 3 works in temperatures from 0 to 50 °C. Because it contains electronics, IQOS should not be exposed to high humidity, and care should be taken not to submerge the device in water.

Switching to IQOS.

Our studies show that the satisfaction of those who switched completely to IQOS is comparable to that of those who continued to smoke cigarettes.* Discover more about our scientific assessment journey.

Discover the studies

IQOS is not risk-free and delivers nicotine, which is addictive. The best decision any smoker can make is to quit tobacco and nicotine use altogether.

* 3-month clinical study conducted in US and Japan with 160 adult smokers each, under near real-world conditions.

Stellar blue and white IQOS 3 DUO holders

Frequently asked questions

Many years of research confirm that harmful and potentially harmful substances produced by burning tobacco are the primary source of smoking-related diseases and problems.

The only sure way of avoiding risks and diseases caused by smoking is not to start smoking in the first place. Aiming to reduce health risks faced by adult smokers who would otherwise continue smoking, Philip Morris International has developed a class of products referred to as electrically heated tobacco products (EHTP). IQOS is one of these such products. This unique technology has the potential to reduce the health risks to which smokers are exposed by smoking conventional cigarettes. The fundamental purpose of developing smoke-free aerosol products is eliminating burning and consequently reducing the quantity of harmful substances.

The result of more than two decades of research, scientific studies comparing IQOS to the reference cigarette, and a USD 9.2 billion research investment is several versions of the IQOS device and a state-of-the-art line of vaporization products that use a tar-free nicotine solution.


The aerosol produced by IQOS contains much less harmful substances than cigarette smoke, by as much as 95% on average. See other sections for a detailed explanation. These figures have been confirmed by measurements performed using high-precision instruments in a laboratory and in accordance with standardized laboratory procedures verified by independent examiners. The significantly reduced quantity of harmful substances is also manifested by their considerably lower absorption and metabolization in the body. This fact has been confirmed by clinical trials performed based on internationally recognized ethical and scientific requirements for conduct of clinical studies.
Even more important, however, is that the main clinical indicators of diseases generally connected with smoking return to their normal values in smokers who switch to IQOS. The drop is so substantial that the values approach the clinical indicators found in persons who have stopped smoking cigarettes altogether.

The section below explains the risks represented by clinical risk indicators.

The findings do not mean that using IQOS is without risks. They show, however, the reduced content of harmful and potentially harmful compounds in aerosol produced by IQOS results in an important decrease in the impact on human health and a lower potential of the onset and development of diseases associated with smoking conventional cigarettes.

Philip Morris International commissions long-term studies and monitors events related to users of its products for the purposes of mapping the long-term effects of IQOS use on health. However, obtaining an unambiguous proof of changes in the population is a long-term effort of clinical research. For that reason, a number of studies with volunteer subjects are still under way. Detailed information on these studies is provided in this article.

Among other methods, a specially designed mathematical model is currently used to assess the potential of IQOS devices to reduce or completely eliminate health risks associated with the use of tobacco products in relation to the age of users. The model indicates that switching to reduced-risk tobacco products represents mainly the prevention of health risks for smokers aged 20 to 30 years, while it tends to reduce the degree of these risks in regard to smokers aged 40 years and older.

It has been demonstrated that using IQOS instead of smoking conventional cigarettes reduces the risk that the individual will experience the diseases commonly associated with smoking cigarettes. It doesn't mean that this risk does not exist; however, it is lower. An IQOS device therefore represents a better choice for health than continuing smoking conventional cigarettes. In 2016, the British Royal College of Physicians stated, "Harm caused by smoking is not primarily due to the use of nicotine as such, but the other components of tobacco smoke. For that reason, it is important to encourage as many current smokers as possible to switch to a smoke-free source of nicotine. This way, significant improvement can be achieved as regards their health and life expectancy". (The source is available here)

According to a Swiss non-clinical study, IQOS stains your teeth significantly less than cigarettes. If your teeth are already stained, however, switching to IQOS will make no difference. The Swiss study was carried out using human teeth and the most common dental materials. Unlike in real-life conditions, the tested teeth were not exposed to other substances which cause staining, such as coffee, tea, and wine.

In addition, an online survey has been conducted in Italy, Japan, Romania, Spain, and Switzerland among 3,157 former smokers who have switched to IQOS to determine the effect of using IQOS on their breath compared to smoking cigarettes. Based on the experiences reported by the respondents, using IQOS rather than smoking cigarettes results in fresher breath.

Currently available data from studies into HPHC exposure reduction show that fully switching to IQOS is not without risks. However, using IQOS represents a lesser health risk than continuing to smoke conventional cigarettes. 
The latest exposure response study (ERS) has been designed to respond to important questions regarding the impact of tobacco heating products in the real-life conditions in which they are used. The ERS is the first large-scope clinical research analyzing the potential of reducing the health risks of smoke-free products to which their users are exposed. The extensive study, which monitored 984 volunteers over six months, measured changes in clinical risk indicators in healthy smokers who have either switched to IQOS tobacco-heating devices or continued smoking their favorite brand of conventional cigarettes. This study lasted six months and yielded the following findings:

  • All of the eight monitored clinical risk indicators measured at the end of the study showed improved values in smokers who switched to IQOS during the study,
  • The majority, specifically five out of eight, of these indicators showed statistically significant differences between groups of IQOS users and a group of those who continued smoking conventional cigarettes.

The results were obtained despite the fact that some of the monitored IQOS users simultaneously continued smoking conventional cigarettes (at a ratio of 30% cigarettes versus IQOS). Apart from the abovementioned eight main clinical risk indicators, a favorable trend was detected in regard to other clinical factors as well. The outcome of the ERS therefore confirms the ensemble of the findings of previous studies, all of which point to a reduction in health risks.

The temperature of aerosol entering the user's mouth is approximately 45 °C. However, the temperature of smoke from cigarettes varies. The temperature the smoke increases more by drawing the smoke and as the cigarette burns more towards its end. The IQOS aerosol is therefore slightly hotter than smoke from a cigarette immediately after it has been lit, but it is a bit cooler than smoke from a cigarette that has been almost completely burned. The sensation of heat also depends on the area of the filter that comes into contact with your lips.
It is a well-known fact that smoking causes numerous respiratory diseases, including asthma, irritation, and damage to the respiratory tract and lung tissue. Cigarette smoke contains more than 6,000 substances, of which about 100 are classified as harmful or potentially harmful, as well as high levels of oxidants. Some of these harmful and potentially harmful compounds are the primary mediators of the impact of cigarette smoke on the respiratory tract and the lungs, as mentioned above. Available data from PMI on IQOS show a significant decrease (95% on average) in the level of harmful and potentially harmful compounds in the IQOS aerosol compared to inhaled cigarette smoke. Switching to IQOS therefore entails lower risk of damage to the organism than smoking cigarettes. Data collected during our laboratory and model studies on animals prove that IQOS considerably reduces inflammation and damage in lung tissue compared to cigarettes. To date, no study has been conducted into the effect of IQOS on the development of asthma. The ultimate proof of the effects of using IQOS on respiratory diseases compared to smoking cigarettes will require further analysis. The results will be available once the product has been on the market for a sufficiently long time.  What is still valid is that IQOS is not without risk, and the best way of avoiding the harmful consequences of smoking is to quit altogether.
There is a scientific opinion[1] that an increase in body weight after stopping smoking is normal. The mechanisms involved in this process are complex, and they have not been fully explained. Smoking cessation likely causes an increase in weight, because the nicotine present in cigarettes increases energy expenditure and suppresses appetite. In most cases, the increase in weight is limited to up to 4.5 kg, and former smokers return to the weight they would have had if they had never started smoking. The increase in weight is therefore much less harmful to health than continuing smoking. Switching from cigarettes to IQOS dramatically reduces the exposure to toxic substances, but it involves a similar exposure to nicotine as smoking cigarettes. Currently available data on the impact of switching to IQOS on weight come from our clinical trials. After six months, switching from cigarettes to IQOS increases body weight and the body mass index on average by +0.71 kg and +0.24 kg / m2 (PMI MRTPA for IQOS, 2018). Hence, switching to IQOS should have only a limited effect on weight. However, the impact of using IQOS on body weight versus continuing smoking requires further long-term analysis. The results will be available once the product has been on the market for a sufficiently long time. What is still valid is that IQOS is not without risk, and the best way of avoiding the harmful consequences of smoking is to quit smoking. If you experience a significant increase in body weight after switching to IQOS or quitting smoking, consult with your physician about your health .In addition, eating a balanced diet and remaining sufficiently active may help stabilize your weight.  References: [1] Aubin HJ, Farley A, Lycett D, Lahmek P, Aveyard P. Weight Gain in Smokers after Quitting Cigarettes: Meta-Analysis. BMJ. 2012;345:e4439
Nicotine shrinks veins and arteries that distribute oxygenated blood through the body. Among other effects, that reduces blood flow in certain parts of the body, including the gums. The blood vessels of younger persons are able to expand to their original size during the time between cigarettes, but their elasticity decreases with age due to the long-term effect of the various toxic substances associated with smoking. Due to the harmful and potentially harmful compounds they regularly inhale, smokers of conventional cigarettes have a demonstrated predisposition for the onset and development of parodontosis and other similar oral diseases. It has been clinically demonstrated that smoking cigarettes has a damaging effect on the oral cavity. In other words, the regular intake of harmful and potentially harmful compounds results in the onset and development of parodontosis. These facts show that it is in theory possible that switching to IQOS may cause temporary gum bleeding in adult smokers, but not as a manifestation of parodontosis or another disease, but, on the contrary, as the effect of a sudden improvement of blood vessels patency in the gums, which increases blood flow and makes the gums more sensitive to irritation. Removing the effect of harmful and potentially harmful compounds on the oral cavity eliminates inflammation and regenerates oral tissues.
Philip Morris International conducts long-term studies to monitor the causes of the onset and development of lung cancer in connection with the use of tobacco products. A recent laboratory focused on the effect of various ways of using tobacco on the lifelong risk of the onset of cancer. In other words, this is the degree of risk that a smoker will develop cancer during his or her lifetime. In the case of cigarette smoke, the risk is commensurate with the presence of numerous carcinogenic substances produced by the burning of tobacco. These chemicals include, among many others, acrylonitrile, butadiene, cadmium, formaldehyde, specific tobacco nitrosamines, and acetaldehyde. In contrast, a study on mice exposed to the long-term effect of different aerosol types has found that IQOS aerosol reduces the lifelong risk of developing cancer by 97.6% compared to cigarette smoke. There is a 95% average reduction in the above-listed substances, and, for example, cadmium was not detected at all. Adult IQOS users therefore face a lower overall risk of onset and development of lung cancer and other smoking-related diseases. Nonetheless, IQOS is not without risks. However, a high number of verified studies and analyses provide evidence that IQOS contains considerably lower quantities and concentrations of harmful and potentially harmful compounds, which makes IQOS a reduced-risk alternative to smoking conventional cigarettes.
IQOS tobacco sticks contain nicotine. Even a small quantity of nicotine has a stimulating effect and may cause an accelerated heart rate. Although this phenomenon is a temporary effect of inhaled nicotine, nicotine should be avoided by people suffering from cardiovascular diseases and other medical complications concerning blood vessels and cardiac activity. 
Among other substances, IQOS tobacco sticks contain glycerol, sometimes referred to as glycerin. Glycerol acts as a moisturizer that helps form visible vapor. Glycerol is also used as solvent and sweetener in various industrial applications. It is considered a safe substance in the standard quantities contained in foods. In the body, glycerol acts as a direct source of energy by being transformed into glycogen (energy storing substance). Higher quantities of glycerol may cause nausea, vomiting, diarrhea, headache, or thirst. The intake of higher quantities of glycerol should be avoided by persons suffering from diabetes, cardiac disorders, and liver or kidney damage. Higher concentrations cause irritation, but glycerol is non-toxic, non-irritant, and non-allergenic under normal conditions.
No tobacco products should be used by people suffering from any health condition liable to be exacerbated by nicotine. Although using IQOS represents lower health risk than smoking conventional cigarettes, tobacco sticks contain specific substances to which some individuals may be sensitive or allergic. That might cause the abovementioned reactions, similarly as the potential overdosing on nicotine. If you experience any lasting adverse health condition, you should visit a physician as soon as possible to consult your specific health issues and potential contraindications for nicotine or any of the substances contained in tobacco sticks. Because the aerosol from IQOS devices contains on average 90-95% less harmful substances that enter the human body, the improvement might cause various reactions, including a change in blood sugar level, better blood flow, and a temporary increase in bleeding from certain blood vessels. In particular, people suffering from Type 2 diabetes should consult switching to IQOS with their physician. However, adult smokers who completely switch to IQOS should expect an improvement in their overall health condition. This is demonstrated by a six-month study that shows that the main clinical indicators of diseases commonly attributed to smoking cigarettes return to their original values after starting using IQOS, where the change is so pronounced that the relevant values approach clinical indicators found in people who have stopped smoking cigarettes completely.
Using smoke-free tobacco products, including IQOS, is a reduced-risk alternative to smoking cigarettes. Despite that, IQOS use may, in rare cases, cause an allergic reaction in persons with a medical predisposition to that effect. In rare cases, users might experience an allergic skin reaction to nicotine, propylene glycol, or glycerol in the form of hives, rash, or itching. Allergic reactions reported during clinical trials assessing IQOS devices were rare. If you experience an allergic reaction, you need to immediately stop using IQOS and any other tobacco product liable to cause your condition. It is recommended that you visit your physician and report a suspected adverse reaction to IQOS and HEETS tobacco sticks to the Philip Morris Slovakia s.r.o. PMI is dedicated to product quality and customer satisfaction, and your report can contribute to our ongoing effort to develop reduced-risk tobacco products.