External factors play a crucial role in the pathogenesis of skin diseases. Other factors that may induce, trigger or exacerbate skin disease then follow. Vitiligo may be related to trauma such as vaccination, radiotherapy, sun exposure, malignancies and their treatment, drugs, psychological factors, and endocrine disease.

External factors play a crucial role in the pathogenesis of skin diseases. They are major players even when there are well established genetic factors. This issue first describes the developments in understanding the main hereditary and nonhereditary genetic modifiers involved in the pathogenesis of UV-induced skin cancer. Other factors that may induce, trigger or exacerbate skin disease then follow. In psoriasis these include injury to the skin, stress, temperature, alcohol, and drugs; in exogenous itch: mechanical, chemical, and environmental factors; in atopic dermatitis: irritants, allergens, house dust mites, and air pollution. Hair diseases are influenced by grooming, heat, chemical agents and climatic exposure. Vitiligo may be related to trauma such as vaccination, radiotherapy, sun exposure, malignancies and their treatment, drugs, psychological factors, and endocrine disease. Cutaneous lupus erythematosus wraps up the list, with environmental risk factors such as ultraviolet light, infections, foods, medications, pesticides and heavy metals. Its comprehensiveness makes this issue a valuable and highly recommended update to dermatologists and allergists.