Beyond its known links to cancer, lung and heart disease, smoking is now thought to be associated with premature skin ageing and delayed wound healing, as well as a number of skin disorders, particularly psoriasis, hidradenitis suppurativa and cutaneous lupus erythematosus.
Smoking and ageing skin
Smoking can accelerate the skin ageing process in the skin. Ageing of the skin means that it droops, develops wrinkles and lines and can become dry and coarse with uneven skin colouring and broken blood vessels (telangiectasia). Smokers can appear gaunt and develop an orange or grey complexion.
Since the 1970’s studies have shown that smoking results in more premature facial wrinkling than sun exposure. Lines around the eyes called “crow’s feet” can develop at an earlier age. Multiple vertical lines around the mouth also occur and are called “smoker’s lines”. These effects continue into old age. By the age of 70 years, smoking 30 cigarettes a day could lead to the equivalent of an extra 14 years of skin ageing.
How does smoking cause ageing of the skin?
It is not certain exactly how smoking causes early ageing of the facial skin. Theories include:
- Heat from the cigarette directly burning the skin
- Changes in the elastic fibres of the skin
- Narrowing of blood vessels (vasoconstriction), which reduces blood supply to the skin and can cause changes in skin elastic fibres and loss of collagen
- Reducing Vitamin A levels and moisture of the skin
Smoking and wound healing
Smoking delays wound healing, including skin injuries and surgical wounds. It increases the risk of wound infection, graft or flap failure, death of tissue and blood clot formation. The reasons for this are unclear but involve:
- Vascoconstriction and lack of oxygen reaching skin cells
- Decreased collagen synthesis
- Delayed growth of new blood vessels within the wound.
Smoking contributes to the development and persistence of leg ulcers, particularly arterial ulcers and diabetic foot ulcers.
Smoking and viral infections
Smoking is associated with a greater likelihood or severity of certain viral infections, including genital warts. If you have genital warts and you smoke, you have a greater chance of developing wart-virus associated cancers, including cervical cancer, vulval intraepitheial cancer, vulval cancer or penile intraepitheial cancer.
Smoking and skin cancer
If you smoke cigarettes, compared to non-smokers you have twice the risk of developing a type of skin cancer called squamous cell carcinoma. There is also an increased risk of oral leukoplakia (precancer) and oral cancer; 75% of cases of oral cancer occur in smokers.
Smoking and psoriasis
Studies have shown that if you smoke you have a higher risk of a scaly skin condition called psoriasis. Psoriasis tends to be more extensive and severe in smokers, particularly if they also have metabolic syndrome. A form of localised psoriasis known as palmoplantar pustulosis
(also called palmoplantar pustular psoriasis) is much more common in smokers than in non-smokers. This condition presents with multiple yellow or brown painful pus-containing lesions on the palms and soles.
Psoriasis is an immune-mediated condition. Smoking is thought to increase the risk of developing psoriasis by affecting the immune system. The nicotine in cigarettes binds to immune cells called dendritic cells and T-cells and may change their function to promote proliferation of skin cells (keratinocytes). Nicotine also binds to keratinocytes directly and helps them divide faster and move upward towards the skin surface.
Hidradenitis suppurativa, also called acne inversa, occurs more frequently in smokers. In this condition abscesses develop in the armpits, under the breasts and in the groin. Like ordinary acne, the hair follicles become blocked, then become inflamed and form abscesses. The nicotine in cigarettes increases the production of a chemical called acetylcholine around the hair follicle, which promotes overgrowth of the upper portion of the hair follicle and thus causes a blockage.
Blood vessels narrow temporarily and eventually permanently on exposure to nicotine, and smoking makes blood clots more likely to develop.
Smoking can aggravate or initiate Raynaud phenomenon. In this condition the arteries supplying the fingers and toes may go into spasm, causing temporary cessation of blood flow. The skin turns through a succession of colours from normal to white, blue and finally red as it rewarms. Usually cold temperature triggers an episode, but nicotine and caffeine are also known culprits.
Secondary Raynaud phenomenon is when there is an associated disorder causing blood vessel spasm or obstruction. Raynaud phenomenon is sometimes a sign of systemic sclerosis, which is an autoimmune disorder, in which the body’s immune system attacks itself, resulting in widespread scarring (fibrosis) and vascular disease. Raynaud phenomenon is one of its first symptoms and can lead to ulcers on the fingertips and toes where the blood supply is poor. Smoking, which is a significant risk factor for vascular disease, increases the risk of developing these ulcers.
Chilblains are also due to vasoconstriction and may be aggravated by smoking, as may frostbite.
Smoking is also responsible for Buerger disease (thromboangiitis obliterans), in which blood clots occur in small blood vessels, and many cases of cholesterol emboli associated with atherosclerosis. It may aggravate the tendency to clot caused by thrombophilia, antiphospholipid syndrome or drugs. Thus those prescribed oral contraceptive medication, perhaps as hormonal therapy for acne, are advised not to smoke.
Cutaneous lupus erythematosus
In the last few years studies have shown a more than ten fold increased risk of discoid lupus erythematosus in smokers. In this autoimmune skin condition, light exposed areas such as the face develop scaly red lesions that can leave scars. One theory that explains how smoking could increase the risk of discoid lupus is that it increases autoimmune activity by activating the lymphocytes (white blood cells) called B-cells and T-cells.
Treatment of cutaneous lupus erythematosus with hydroxychloroquine and other medications is less effective in smokers.
Not surprisingly, conditions affecting the mouth tend to be more common in smokers. These include:
- Oral candidiasis (thrush)
- Oral lichen planus and erosive lichen planus
- Black hairy tongue (lingua villosa nigra). In this condition the surface of the tongue has elongated hair-like processes and is yellow, brown, green or black due to bacterial overgrowth. The condition is due to soft diet, poor oral hygiene, lack of saliva and smoking.
- Nicotine stomatitis
- Hairy leukoplakia associated with HIV infection
- Gingival enlargement
- Actinic cheilitis i.e., dry peeling lips due to sun damage
Rather surprisingly, aphthous ulcers are less common in smokers.
Other skin diseases
There is a general observation that smokers tend to be more severely affected by many skin diseases than non-smokers and various conditions appear more difficult to treat effectively in smokers.
Effect of smoking on medicines
Polycyclic aromatic hydrocarbons from smoking induces CYP1A2 enzymes in the liver. These enzymes destroy toxins. The result is that smokers need higher doses of many medicines compared to non-smokers to achieve the same result. These include insulin, pain relievers, antipsychotics, anticoagulants, caffeine and alcohol.
Alcohol intake and caffeine intake are on average double in smokers. This tolerance of alcohol and caffeine is quickly lost when a smoker stops smoking. Previously tolerated amounts of alcohol and caffeine can result in unexpected toxicity.
Alcohol ingestion can also lead to smoking more.