If you skin is dry this can cause bumps and itchy skin. Nerves can create hives. To much sun. Some materials that rub against your skin, like polyester or nylon.
Please consider being in contact with synthetical material. Material like spandex can prevent your skin from breathing optimally, the warmth cannot escape. Ithches and bumps can be caused by this, maybe try a cotton shirt or trousers!
Itchy bumps on your legs and arms may be an allergic reaction from a recent food product you ingested, lotion, noxious weed, recently prescribed medicine or bites from insects, especially mites.
Several things could cause itchy bumps on your skin; but I would consider looking into the possibility of an allergic reaction you may have had. Are you using a new lotion or new laundry detergent? In the meantime, I would put a hydrocortisone cream on it and seek medical attention if it gets worse.
