Wa'alaikumsalam! Adik susah sikit nak tau exactly sebab apa (panas, allergic, atau hives), kena tengok pattern dia la, kalau muncul after makan certain food, atau lepas pakai baju/produk baru, atau just terik-terik, tu dah clue sikit. A few of us went through this, and honestly the safest way is to check dengan doctor sebab kalau hari-hari makin teruk, better to get proper diagnosis ye, especially if ada demam or bengkak-bengkak. Dalam masa tu try cooling baths, loose clothing, and skip laundry products yang strong. Jaga-jaga je dulu, and do see the doc to be safe!