It can be hives or any other skin trouble. Hives can occur in allergies to food, medications, cosmetics, soaps, and detergents, animal bites and pet danders etc. Usually hives occurs with itching, burning and stinging pain. If your experiencing this try to identify the cause of your problem.  However in many cases exact cause cannot be identified. But such rashes fade away when allergy causing agent is removed. They can last from few minutes to few hours generally. Secondly your problem can also be dermatitis which in some cases begins as small blisters and spreads.  It can also be caused by allergic agents same as hives. Clinical examination of rash, location,  appearance,  type of rash and symptoms can help us determine the exact cause of the problem.consult  a nearby physician or a dermatologist if problem persists or recurring. Consult a homoeopathic physician if available for treatment if problem persists.