Smoking is well-known for having detrimental effects on human health.
As well as carcinogens from cigarettes raising the risk of chronic disorders, cancer and premature death, nicotine also increases the likelihood and severity of dermatological diseases such as skin cancer, psoriasis and alopecia [1,2].
The effect of smoking on the skin microbiome is one area that has remained relatively unexplored, but research suggests that smoking may also impact our skin’s microbial communities. This could potentially disrupt the normal functions of the skin microbiome and contribute to the harmful effects of smoking on our skin [3].
Want to learn more? Let’s dive in…
The effects of smoking on the skin microbiome
New research, led by Katherine G. Thompson of Johns Hopkins University, has revealed significant differences in skin microbiota composition across three groups: current, former and non-smokers [3].
Smoking was associated with significant changes in overall microbial diversity and the relative abundance of many bacterial types on the skin (shown using samples from the cheek and forearm). Smokers had higher numbers of Actinobacteria species, for example, but lower numbers of Fusobacteria species when compared with non-smokers, with numerous other bacterial types also varying in abundance across the two groups [3].
Although these bacteria are normal inhabitants of healthy human skin, it is possible that the disruptions seen in smokers could be hindering the normal functions of the skin microbiome. We’ll circle back to this later, but this could have a knock-on effect on our skin health – for example by disrupting the protective skin barrier or other physiological functions.
Reassuringly, when comparing smokers and former smokers, it was found that fewer bacterial types were enriched or depleted in the former smokers – this may suggest that some of the skin microbiota disruptions associated with smoking may be reversible.
What else do we know?
Unfortunately, the impact of smoking on the skin microbiome remains a relatively unexplored area. However, work by other researchers has touched on it in brief, and we may be able to draw parallels from work on the microbiome of other bodily areas.
Artificial intelligence also finds smoking-induced variation…
A group of researchers recently used an artificial intelligence (AI) model to demonstrate skin microbiome variations in association with smoking habits (as well as other factors, such as age – see our previous article on the AI study) [4].
The AI model was able to predict whether an individual was a smoker or a non-smoker based on their skin microbiota. A smoker was characterized by higher abundances of 11 bacterial types – or ‘genera’ – such as Brevibacterium, Lactobacillus and Campylobacter, while 9 types, such as Faecalibacterium and Bacteriodes, were indicative of a non-smoker when higher in abundance. This adds to the bank of evidence that smoking is associated with disruptions in our normal skin microbiota, which could be affecting the way the skin microbiome – and subsequently skin itself – functions [4,5].
Smoking and the oral microbiome…
The findings of the new research also align with studies investigating the oral microbiota in smokers, which suggest that smoking has similar effects on the microbiota of the mouth [5,6].
For instance, the overall oral microbiome differed between current smokers and former and non-smokers. Current smokers were observed to have a disrupted skin microbiota with lower numbers of bacterial groups such as Proteobacteria compared with non-smokers, but no difference was observed between former and non-smokers – again suggesting the potential of the microbiota to recover.
The effect of smoking on the oral microbiome has been attributed to the direct effect of toxicants, impaired immunity and the depletion of oxygen associated with smoke inhalation – mechanisms that may also be at play in the skin [6].
Cannabis and the oral microbiome…
An association has also been found between cannabis smoking and oral microbial dysbiosis. In cannabis smokers, oral bacteria such as Streptococcus and Actinomyces were present in higher numbers, while populations of bacteria such as Neisseria were reduced [7].
Why do these changes this happen?
Smoking could be influencing our microbial composition via direct exposure to bacteria contained within cigarettes, or though physiological changes that can impact our immune system.
Bacterial species such as Acinetobacter calcoaceticus and Pseudomonadaceae fluorescens are found in fresh tobacco leaves, and cigarettes themselves contain many different bacterial types, ranging from soil microorganisms and harmless bacteria to potential human pathogens [8]. Differing microbial communities in smokers may therefore arise due to direct exposure to bacteria in cigarettes.
The differing bacterial community in smokers could also be attributable to the immunosuppressive nature of tobacco impacting our body’s ability to defend itself against new bacteria. Tobacco has been shown to affect our immune system on several levels, for example by reducing the number of certain types of immune cells and impairing their defensive function. By hindering the efficient clearance of bacteria, this can permit the growth of new species and change the microbial community [8].
What does this mean for skin health?
Exposure to cigarette smoke is a well-known contributor to premature skin aging, but it has also been shown to induce various skin diseases, such as dermatitis, psoriasis and skin cancer [9].
As mentioned, more research is needed to understand how smoking-induced microbial changes feed into these dynamics and impact skin health. However, it is clear that the microbiome does not remain passive in many pathological processes, and that its modification often contributes to – or plays causative role in – many pathophysiological processes [8]. This means that any disturbance to our skin microbiome balance that disrupts the relative numbers of commensal (harmless) and pathogenic (harmful) bacteria might have knock-on effects for the health and functioning of our skin. For example, by triggering or worsening skin conditions or even systemic disease across the rest of the body.
Previous work has already shown clear links between altered skin microbial composition and numerous skin disorders, such as rosacea [10], psoriasis [11,12] and atopic dermatitis [13].The skin microbiome is also thought to mediate physiological changes in our skin that are associated with genetic factors such as aging [14], as well as lifestyle conditions such as pollution [15] (see our recent article on the skin interactome for a full breakdown of how these factors work together to influence the condition of our skin).
In line with this, one interesting study on cigarette smoke has suggested that smoke as an urban pollutant can worsen the damaging effects of air pollution on the skin [16]. The researchers found that skin microbial networks significantly mediate the adverse effects of air pollution on skin health, and that a smoking lifestyle deepened the negative effects of pollution stress on the facial skin microbiota.
So, it may indeed be that smoking-induced changes in our skin microbiome impact its ability to preserve and regulate our skin condition.
Drawing parallels
Smoking-induced microbial changes and intestinal disorders
One area where the impact of smoking on microbial composition has been linked to negative health consequences is the gut.
Here, smoking-induced changes in the microbiome have been linked to increased incidence and severity of certain intestinal disorders. For example, the intestinal microbiota is known to have an important role in regulating the intestinal environment – changes to the relative abundance of certain bacteria within this microbial community have been linked to several gut-related diseases, such as IBD, colorectal cancer, Crohn’s disease and ulcerative colitis [18].
Taking Crohn’s disease and ulcerative colitis as examples, differences in the intestinal microbiota have been found in patients with these diseases compared to healthy individuals. Cigarette smoking leads to microbial imbalances in the gut and worsens the development and severity of Crohn’s disease. Yet when it comes to ulcerative colitis, smoking actually improves symptoms [17–19] – perhaps because cigarette smoke cannot differentiate between ‘good’ and ‘bad’ bacteria. However, it remains to be determined whether intestinal microbiota dysbiosis contributes directly to the development and severity of intestinal diseases, or is the result of the altered environment within intestinal tract.
Future work
So, although there is much more work to be done to fully elucidate the effects of smoking on the skin microbiome and what this means for our skin function and health, current evidence shows that smoking does indeed impact our skin microbiome.
Future studies are needed to help us understand the significance of these microbial disturbances for the physiology of the skin and other organs, as well as their role in the development of skin and other systemic diseases.
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References
- https://pubmed.ncbi.nlm.nih.gov/20620754/
- https://pubmed.ncbi.nlm.nih.gov/34377115/
- https://www.jaad.org/article/S0190-9622(20)30126-2/fulltext
- https://www.nature.com/articles/s41598-021-83922-6
- https://www.nature.com/articles/ismej201637
- https://pubmed.ncbi.nlm.nih.gov/25012901/
- https://www.thelancet.com/journals/ebiom/article/PIIS2352-3964(21)00495-3/fulltext
- https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-019-1971-7
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8330869/
- https://www.ncbi.nlm.nih.gov/pubmed/31502207
- https://www.frontiersin.org/articles/10.3389/fmicb.2019.00438/full
- https://onlinelibrary.wiley.com/doi/abs/10.1111/bjd.17931
- https://www.sciencedirect.com/science/article/pii/S0022202X17329603
- https://www.frontiersin.org/articles/10.3389/fmicb.2020.565549/full
- https://journals.asm.org/doi/10.1128/mSystems.00319-21
- https://journals.asm.org/doi/10.1128/mSystems.00319-21
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8245763/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4991341/
- https://onlinelibrary.wiley.com/doi/full/10.1111/apt.15774
