Treating hives. Be sure a doctor has seen your rash and it is definitely hives. People who think they have hives may have other rashes. If you have hives for more than 6 weeks, they are called chronic. If they are mild and you feel otherwise well, you can start by trying to control them with antihistamines that are sold otc:cetirizine/fexofenadine/loratidine/benadryl. H2 blockers sometimes help also-ranitidine eg.