Eczema is an intensely itchy skin inflammation reaction caused by various internal and external factors. It is categorized into three phases: acute, subacute, and chronic. 1. Acute eczema: Initially, the skin lesions appear as numerous, densely packed millet-sized papules, vesicopapules, or small vesicles with a reddish base that gradually merge into patches. Due to scratching, the tops of the papules, vesicopapules, or vesicles break open, leading to distinctive punctate exudation and minor erosion with unclear margins. If secondary infection occurs, the inflammation becomes more pronounced, possibly forming pustules, crusts, folliculitis, and boils. There is severe itching. Commonly affected areas include the head, face, behind the ears, extremities, scrotum, and perianal region, often symmetrically distributed. 2. Subacute eczema: Following the reduction of acute eczema inflammation, skin lesions primarily consist of small papules, crusts, and scales, with only a few vesicopapules and erosions, yet intense itching persists. 3. Chronic eczema: Often, chronic eczema results from reoccurring episodes of acute and subacute eczema that do not resolve, or it may start as chronic eczema. Characteristics include thickened, infiltrated skin at the affected sites, which tend to be brownish-red or have pigmentation, a rough surface covered with scales, or crusting caused by scratching. There is severe itching. Common sites include the lower legs, hands, feet, elbows, knees, genitals, and anus. The duration of the disease is variable, it is prone to relapse, and is often long-lasting without resolution.