Fairly certain it is herpes zoster.
Hello,
It can be insect bite, hives or an allergic reaction. If it is present on the trunk and there is significant pain then herpes zoster should be ruled out. Do not use any cosmetic products at the sites. You can apply some calamine lotion at the rash as it will help in soothing the skin and wear cotton clothes. You can take some OTC oral antihistamine medications like Benadryl or Claritin and see if it helps.
For mild-moderate symptoms a weak steroid may be used (e.g. hydrocortisone as dermacort), whilst more severe cases require a higher-potency steroid (e.g. clobetasol propionate, fluocinonide). But they are available under prescription and should be taken only after consulting a dermatologist.
I hope it helps. Take care and regards.