If rash looks like red bumps or pimples (white-heads) on the skin, then it can be folliculitis - staphylococcal infection of hair follicles. Bumps are red, and some may have white heads. The cause may be tight clothes, or spreading of staphylococci from your own skin (if you're staph carrier) or from someone's other skin (being either a carrier or having an active infection). Folliculitis can be treated with over the counter antibacterial ointments. It can go away without any treatment, if you wear airy clothes and wash all clothes, towels, bed lining you've used recently.
If bumps are like blisters, which come in small groups, and occur near vaginal mucosa, then it can be herpes.
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