Hello, Welcome to HCM. I understand your concern. This is due to urticaria because of allergy to something. It may be anything like pollen, woolen cloth, mattress, dust, animal fur or something you might have eaten and allergic to you. It is most of the time very difficult to arrive at the conclusion on what is the cause of allegy. Take Levocetrizine tablet once a day for 2-3 days. chlorepheniramine tablet can also be taken 2-3 times a day but it may cause some sedation. Refrain from scratching excessively. Apply steroid cream like betamethasone cream locally if it is very itchy. Your rash should resolve in a few days. Hope this will be helpful. Thanks for using HCM. Take care.