Blemishes on the buttocks are typically caused ... However, if you have a very large, painful pimple or a cluster of large pimples on your butt, it's more likely that you have a boil (skin abscess).

Pimples stem from clogged hair follicles, while herpes sores are viral blisters that break into painful ulcers. Also, pimples appear in hairy areas, while herpes sores form on mucous membranes and ...