The causes and symptoms of skin diseases also vary. There are different types of allergic dermatitis, and each type has its own symptoms. Contact dermatitis is caused by inflammation of the skin at the site of contact with an external substance. Contact dermatitis is usually divided into primary irritant contact dermatitis and allergic contact dermatitis, where the patient’s lesion status is not fixed and symptoms such as edema, blistering, papules, and vesicles may occur. Neurodermatitis Neurodermatitis, also known as chronic lichen planus, is triggered by a patient’s neurological dysfunction and can recur or worsen when the patient is in an emotional state or anxious, or after consuming alcoholic beverages. Typical symptoms of neurodermatitis are itchy skin and mossy lesions on the patient’s skin. Tanning dermatitis Tanning dermatitis, as the name implies, is caused by sun exposure and may be caused by exposure of the skin to ultraviolet radiation from the sun. Patients with solar dermatitis have a variety of lesions, which can take the shape of erythema, blisters, vesicles, and moss, and are divided into various types such as plaque, erythema, and eczema. Seborrheic dermatitis usually occurs in areas of the body where the sebaceous glands are densely distributed, such as the scalp, face, or chest. Most commonly, seborrheic dermatitis occurs on the skin of the head, where red patches and white flakes first appear on the scalp, and then worsen to a foul odor, with oil leaking out of the skin and crusting over. Some obese people tend to be more prone to seborrheic dermatitis. Cosmetic dermatitis This skin inflammation occurs when people have an allergic reaction to the cosmetics they often use in their daily lives, or when they are exposed to sunlight or other irritants after using cosmetics for the first time or again.