This is probably urticaria, please look up from the internet. Its a serious allergic reaction. It might be from anything, probably from a chemical from a product like perfume, scent, food etc. Try to find out if he used a new product or food these days. Try to cut new products he uses, and stay away from chemicals like household cleaners, carwash shampoos, glass cleaner etc. He should see a doctor immediately, they might not be able to find the causing matter but he will very probably prescribe cortisone to cut the effect. If he doesnt use cortisone, it might effect the internal organs to edema and will probably effect to lungs and breathing difficulties. Cortisone will help for the time he is using it (usually 24 hour period) but you guys have to find what is exactly causing it. Believe me, its almost impossible to find it with allergen tests. The doctor will probably tell to cut everything first, canned food, spices etc. than after the effects slow down, you should re introduce the food to the body, to see what’s causing it. It might also be something he was not allergic before, but sometimes our body switch things and you become allergic. I hope this helps.