Neurodermatitis, also known as chronic simple lichen, is a common chronic inflammatory skin disease characterized by paroxysmal severe itching and lichenoid skin changes. Its main causes may be related to various internal and external factors such as neuropsychiatric factors, gastrointestinal dysfunction, endocrine disorders, diet, and local skin irritation. It commonly occurs on the neck, elbows, lumbosacral area, inner thighs, perineum, and around the anus. The skin lesions are characterized by pinpoint or rice grain-sized polygonal flat papules that are pale red, tan, or normal skin color, with a hard and glossy texture. They may be covered with a small amount of scale and, over time, can merge into large plaques, leading to thickened, rough skin with lichenoid changes.

Allergic dermatitis is an hypersensitivity reaction skin disease caused by contact with various allergens, characterized by diverse skin lesions such as erythema, papules, vesicles, swelling, and itching, which can occur all over the body. However, localized allergic dermatitis, if treated improperly or not treated in a timely manner, or due to repeated scratching, can potentially develop into neurodermatitis.