thanks for posting the query. this is Urticaria which is caused by allergy due to lot of factors including physical exposure to allergens like dust, mites, pollen, drugs, sun or cold exposure, food allergy, pets etc. we can do a patch test to find the cause or food allergy test also. medications like antihistamines like fexofenadine and cetrizine is advised and if it is severe short course of oral steroids also along with topical calamine like soothing lotions. consult a dermatologist for further course of action.