So-called “mud dermatitis” is also known as frictional lichenoid eruption or juvenile papular dermatitis or. It is an inflammatory skin disease commonly found on the back of the hands in preschool children. The etiology of the disease is unknown. It is thought to be related to mechanical irritation and sun exposure because of a history of playing with mud, water, rough objects or toys before the onset of the disease. Other scholars believe that it is related to viral infection. The disease is most common in the summer and autumn, and is most common in preschool children. The lesions are mostly found on the back of the hands and may spread to the wrists and forearms. The rash is mostly uniform mossy corn-sized papules, which may be densely packed, mildly pruritic, and skin-colored or red. The prognosis is good. The diagnosis is not difficult based on the patient’s age of predilection, location, and characteristics of the lesions. It is sometimes necessary to differentiate from contact dermatitis and papulopustular acrodermatitis in children. In the former, there is a clear history of exposure to allergenic substances, the lesions are polymorphic and pruritic, and the onset is independent of age and season; in the latter, the lesions are large and flat, the rash is inflammatory and pruritic, and may be accompanied by enlarged lymph nodes and liver lesions. Avoiding adverse stimuli and reducing friction as much as possible are the best preventive measures. Treatment is based on topical medications, and the administration of glucocorticoid creams can mostly relieve.