I developed some itchy bumps first underarms and then they spread to my arms and neck and thighs they are very itchy at night times , i had uti too.?

Allergic reaction?: Itchy rashes are usually allergic reactions, but sometimes are from skin infections. Antibiotic allergy can cause an itchy rash, sometimes after the antibiotic is already finished. People who have a history of eczema can have itchy rashes appear off and on. Sometimes there are skin infections like folliculitis, shingles, pimples, impetigo, etc... A doctor can evaluate to see what it all might be.