Summer is here, and so is lichen planus. I saw several patients with lichen planus in the clinic today, all of whom came in with yellowish-brown or dark brown patches all over their bodies with itching. Pemphigus foliaceus, commonly known as sweat patches, is a chronic, mild inflammation of the superficial stratum corneum of the skin that is often asymptomatic. The damage is characterized by scattered or fused light-colored, or chaffy flakes on the colored areas, which occur on the chest, abdomen, upper arms and back, and sometimes spread to the face and neck and other areas. Etiology The disease is caused by a lipophilic yeast – Malassezia furfur, which is a common putrefactive parasitic bacteria on normal human skin. Clinical manifestations It starts as many tiny spots, and soon the area of desquamation on it expands and fuses into a ring and visible discolored spots. The color of the damage varies with the patient’s skin tone and is related to sun exposure and severity of the disease. Sometimes it may appear as yellowish-brown or dark brown patches, or light gray on dark skin, making it extremely difficult to identify. Sometimes they are located around the pores and appear as papular lesions with little inflammatory reaction, preferably on the chest, back and abdomen. Diagnosis According to its clinical manifestations, dander to 10% potassium hydroxide solution direct smear to find curved or arc-shaped yeast filaments or round spores, the disease can be diagnosed. Differential diagnosis 1, vitiligo Mainly for patches of skin pigmentation loss and white, its edge can have pigmentation. Generally no flaking, no itching, no excessive sweating after aggravation history, etc., to check the bacteria lasting negative, etc. more help to distinguish. 2, rose furfur The disease starts with mother spot, quickly spreads to the whole body, is red oval spot, central has furfuraceous scales, its long axis and skin pattern direction, check fungus negative. 3, erysipelas often confined to the axilla, under the breast and groin and other skin folds or folding parts, lesions slightly red in color, scales do not easily fall off, 10% potassium hydroxide liquid smear is not easy to find erysipelas, need to do special staining to be found.