He is having Acute Urticaria.
This occurs due to an allergic reaction to something that he ate or something that he is in contact with.
You should check out whether he has started any new medicines or food supplements during this period that he is having the attacks. Also see whether he has been taking any new types of foods like cheese, some types of meat, nuts, etc. It could be due to some new detergents or cosmetics that he is using, or some new type of soap,bath soaps, perfumes, etc. Link
If you do find anything which could be the cause, then you should ask him to avoid this. If he continues to use whatever is causing this attack, he will not recover easily, hence it is most important to identify the possible cause. Continuing use of the allergen may be causing persistence of the condition.
The primary treatment of such urticaria is with an antihistaminic like Benadryl cap (OTC). He should continue in the dose given. Usually this alone will be sufficient to control his symptoms. You should give it more time. At the same time if you can identify any allergen and discontinue it that will help. Urticaria or hives however can coninue long after the person is not in contact anymore with the cause, it can continue for weeks. However, if it persists for more than a week or 5 days, then you need to consult your family physican or a dermatologist preferably.
You should read up here: http://dermnetnz.org/reactions/urticaria.html http://www.emedicine.com/emerg/topic628.htm
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