The condition of having many itchy bumps on the buttocks may be a result of a certain allergic reaction in that area. But the most common type of this allergic reaction may be mite dermatitis, or what is called papular urticaria, which is mostly likely due to mite allergy or mosquito bites, etc., resulting in a local inflammatory reaction, and in some cases, a certain amount of inflammatory exudation and blistering. Of course, there is also the possibility of hives in the area, and the occurrence of hives may be due to local friction or mechanical compression of the area, so the formation of artificial hives. It is also possible that there is some infection in the area, so that a lot of bumps are formed, such as the appearance of bacterial infection and the formation of folliculitis, if these inflammatory reactions are not too obvious, then it may also cause some itching symptoms.