If raised bumps or welts appeared on your skin a few hours or even in some cases, a few minutes after eating or drinking a new item or taking a new type of medication, then it is possible that it is an allergic reaction.
White bumps can be a sign of contact dermatitis. This is an allergy caused by something touching or rubbing your skin. Possibly a new laundry detergent. Bumps can also be red and itchy.
In rare cases only white bumps appears on body due to allergic reaction. You can find out the cause by trial and error. Just check up whether it increases when you take some special food like prawns, egg, or other shellfish or while taking any medicine.
