I was diagnosed with hives. disappeared in 4 days with antihistamine use , could this be a sign of hiv infection?

Not specifically: Hives are called urticaria and can come from many, many reasons. Ofter we are unable to identify a cause. If they improve with anti- histamine that is good. The real truth is after you stop using the antihistamine do they recur. If they recurr many times over a period of time they can be classified as "Chronic Urticaria". When we see a patient with urticaria we think of many causes!