Smoking causes acne in women, reported the Daily Mail . But rather than normal acne, it causes non-inflammatory acne, characterised by “blocked pores and large blackheads but less inflamed spots than normal acne”, the newspaper explained. The report is based on the findings of a study of 1,000 women that found that smokers who were acne sufferers in their teens were four times more likely than non-smokers to develop acne in adult life.
This story is based on a letter in a medical journal discussing the findings of a cross-sectional study. Without full details, the quality of the study cannot be fully assessed. Cross-sectional studies, however, cannot establish causation. At best, the study has highlighted a link between smoking and acne that will need further investigation. The findings are not robust enough to suggest that smoking is a cause of acne.
Where did the story come from?
The study was carried out by Bruno Capitiano of the Paediatric Dermatology department, and colleagues of the Laboratories of Skin Physiopathology, Clinical Pathology, Immunology and Histopathology, of San Gallicano IRCCS, Rome. It was published in the peer-reviewed medical journal British Journal of Dermatology .
What kind of scientific study was this?
The article is a letter where the authors have discussed their recent cross-sectional study into smoking and acne. The researchers describe a form of ‘non-inflammatory acne’ that they have seen through their clinical practice experience.
The article suggests a cross-sectional study was conducted, but does not provide many details about the study that was carried out. It says that women aged from 25 to 50 years old, who were mothers or were accompanying children to a children’s skin clinic were randomly enrolled to the study to give a group of 1,000.
The participants were asked questions about smoking habits, acne as a teenager, and hormonal imbalance, and they were examined for the presence of acne and for signs suggestive of an excess of male hormones. The acne was classed as being inflammatory (if there was a predominance of red spots around the jaw area) or non-inflammatory (if there were mostly blocked pores and blackheads on the cheeks and forehead). The researchers compared the prevalence of acne between smokers and non-smokers in the sample.
What were the results of the study?
The researchers found that 18.5% of the total 1,000 women had acne. When the group was divided into smokers and non-smokers, 41.5% of the smokers had acne compared with only 9.7% of non-smokers.
The researchers report that when they asked about acne as a teenager, 47% of the female smokers who were affected when they were young had acne now, compared with only 18% of non-smokers. They concluded that of women who had acne as teenagers, smokers were four times more likely to suffer acne as an adult compared with non-smokers.
What interpretations did the researchers draw from these results?
The authors conclude that non-inflammatory acne, which differs from the normal form of adult acne, is more common in smokers. They say that predisposed females, that is, those who had acne when they were young, are more likely to experience acne in adult life if they smoke. They discuss possible explanations for this, such as nicotine and other chemicals in smoke increasing the levels of skin cell turnover, causing constriction of blood vessels, a lack of oxygen to the skin, and causing oxidation reactions that alter the content of the oily substance (sebum) produced by the skin.
What does the NHS Knowledge Service make of this study?
This article presents findings of the observations in female smokers attending a clinic in Italy. Although smoking may be a contributing factor towards acne, it cannot be concluded from this report alone that it is a cause:
- The time relationships between the women starting smoking and when they developed acne are not known. It is not known how the development of acne relates to the length of time smoked or to the number of cigarettes per day; it is also not known how ex-smokers or those who had never smoked were considered by this study.
- It is usually very difficult to pinpoint an exact cause for acne. There are many possible causes and these may include hormonal, genetic, environmental, and lifestyle factors, other medical conditions or medications may also have an effect. Although this study attempted to take some of these into account, for example, by excluding those with possible hormone imbalance, it is not certain that other factors are not influencing the results. As the study details were limited, there is no information on how suspected hormone imbalance was determined (from clinical appearance, by asking the patient about their medical history or through further investigations).
- Even if smokers were found to be more likely to have acne, it is not known that this relates to smoking or to other factors that may be linked to smoking.
- The clinical features of acne may fluctuate over time, sometimes inflammatory spots are predominant on the skin, other times blocked pores may be more apparent. Therefore, if women were assessed at one point in time only, their classification into one of the groups may not be very accurate.
- Finally, as these results are from one Italian clinic only, the findings of this study cannot necessarily be generalised to other countries.
Sir Muir Gray adds...
There are already plenty of good reasons not to start smoking, or to give up if you do. This may be one more, and one of particular relevance to a group whose smoking remains very high, probably mainly because of weight worries. Tempting though it would be to use this piece of evidence, a letter is not sufficiently robust evidence for immediate action.