Exposure to ultraviolet (UV) light, most commonly from sunlight, is generally considered the modifiable risk factor attributable to the greatest number of skin cancers.[1][2] In general, the risk of BCC and SCC increases with greater cumulative sun exposure, whereas the risk of melanoma increases with frequency of sunburns.[3] Tanning beds are also a significant source of UV light and their use is associated with a higher risk of skin cancer, both NMSCs and melanoma.[4][5][6]
Skin color has a strong relationship with skin cancer risk, since melanin absorbs UV rays, providing some degree of protection against its effects. As a result, the risk of melanoma is several times higher among light-skinned compared to dark-skinned people.[7]
Several drugs and even food-derived compounds are classified as photosensitizing, meaning they increase the skin’s sensitivity to UV light and potentially increase the risk of skin cancer when combined with sunlight exposure.[8] Examples of photosensitizing medications are tetracycline, doxycycline, quinolones, and thiazide diuretics.
Finally, because the immune system plays an important role in inhibiting skin cancer development, the use of a number of medications with immunosuppressive effects are associated with a higher risk of skin cancer. This includes TNF-a inhibitors,[9] methotrexate,[10][11] cyclosporin,[12][13] and tacrolimus.[14] As a result of this phenomenon, organ transplant recipients who require immune-supressing medications (to prevent organ rejection) are at a much higher risk of SCC than the general population.[15]