Redness, swelling and walking pain on both sides of the butt crack are usually caused by intertriginous rash, chronic eczema, ringworm and other diseases. 1. Interfluvial rash: it is caused by the skin in the folds rubbing against each other, in addition, the local humidity can also cause this disease. The skin lesions occur in the armpits, buttocks and other folds, the onset of the initial stage, the skin lesions are clearly defined red spots, and swelling is obvious, with the development of the disease, localized erosion, oozing, accompanied by pain and other discomforts, walking and friction, pain aggravated. 2. Chronic eczema: it occurs in the hands, feet, breasts, anus and other parts of the body, some patients can also occur in the buttocks on both sides of the crack, the skin lesions for the infiltration of the dark red spots on the pimples and scales, which can be accompanied by varying degrees of mossy changes, when walking and friction, it can be itchy, pain and other discomforts. 3. Ringworm: It is a skin disease caused by fungal infection, mostly seen in the groin, perineum, buttocks and buttock cracks on both sides and other parts of the body, the lesions are red papules or small blisters at first. Following, the formation of scales, and spread to the surrounding, the surface is generally no ooze, the patient may be conscious of itching, when walking friction to the affected area, there can be pain. In addition, there are many other reasons that can cause redness on both sides of the butt crack and walking pain, it is recommended to consult a doctor in time to identify the cause of the disease, and then receive treatment as soon as possible.