Infant skin is thin and tender, and a rash will appear when it encounters slight stimulation. Red spots on the buttocks of infants are commonly seen in the following situations: 1. Diaper dermatitis: Diaper dermatitis is a common skin inflammation that occurs in the diaper area of infants. The main manifestations are erythema, papules and sometimes blisters in the diaper area. Some scholars believe that diaper dermatitis is caused by ammonia stimulating the skin in the diaper area. 2, bite dermatitis: refers to insects with blood-sucking peckers or stinging mouthparts bite the skin, sucking blood from the human body, while sucking blood will be injected into the body of the poisonous juice or saliva thus causing skin inflammatory reactions. The main manifestations are scattered erythema, papules, and bumps at the site of the bite, accompanied by itching or burning sensation. For diaper dermatitis you should keep the diaper area dry, wash and change diapers regularly, use less irritating detergents, and reuse them after scalding with boiling water and drying in the sun. For bite dermatitis, you should improve environmental hygiene, eliminate insects, strengthen protection, wear long sleeves when entering forest areas or the wilderness, and take a bath and change clothes in a timely manner. In the case of severe rash, you should seek medical attention.