According to the text, skin diseases are not just a protective cover, they are an organic system that regulates body temperature and sensation, and prevents substances from penetrating the body. Some of the most common skin diseases include eczema, urticaria, psoriasis, fungal infections, and bacterial infections. Atopic dermatitis is considered the most common, affecting every twentieth person and characterized by chronic inflammation and itching. Treatment for this condition is crucial for managing symptoms. Other common skin diseases include acne, eczema, psoriasis, erysipelas, and melanoma. These conditions can be identified by their symptoms and prompt treatment can lead to favorable outcomes. Skin diseases can also have a significant impact on a person's mental well-being, especially those that are easily visible on exposed areas of the skin.