What is the best thing to help buttock rash and itch?

Depends entirely.... ..On what is causing it. Could be an allergic reaction, or a viral, bacterial, or fungal infection, or a drug reaction, or other things. No way to know the best treatment until you know the cause. See a dermatologist.

Related Questions

I am experiencing buttock rash, genital itching and genital pain. The following also describe me: Vaginal itching, Skin redness or irritation, and...

Need to examine. It is not feasible to provide a meaningful opinion without taking additional history, physical examination and may be some tests. It would be prudent to see your doctor. What you described is suggestive of herpes.