Some red bumps on the waist may be caused by contact dermatitis, urticaria, eczema and other diseases. 1. Contact dermatitis: caused by skin contact with exogenous substances that irritate the skin or trigger an allergic reaction. If the patient’s waist skin comes into contact with underwear, bathing suits, belts, etc., erythema, edema, red bumps and other symptoms may appear. 2. Urticaria: The appearance of urticaria may be related to infection, food and drugs, mental, physical and other factors, the patient’s skin will appear uneven red bumps, all parts of the body can appear. 3. Eczema: the cause is mostly related to genetic, immune abnormalities, endocrine and metabolic diseases and other factors, patients will appear erythema, papules, papules and other symptoms, some patients will grow some red bumps on the waist. There are many reasons for some red bumps on the waist, it is recommended that patients go to the hospital to clarify the cause of the disease.