Hi. Welcome to HCM You seemed to have developed an allergy to something. A possibility could be some food item present in your burger or anything else you consumed. Allergies can develop to almost anything, could be dust, pollen, pets, insect bites or some plants etc. Any medication you are on? New cosmetics? You may not have noticed if you were exposed to any of these but in any case you can treat it with a course of antihistamines like levocet/ fexofenadine daily or about 5 days and stop. Apply a calamine lotion to soothe the skin. if the rashes are severe or spreading apply a mometasone cream for 5-7 days and check. If you have severe itching, rashes spreading over body , breathlessness or severe symptoms, visit the ER and get an antihistamine and cortisone shot as they advise. Try and keep a note of anything that aggravates it. Anytime you develop a similar rash again, try to keep track of what could have caused it and avoid such factors that you may be allergic to. Since you dont have any itching, watch for symptoms like fever, pain, burning, blistering etc and consult a doc if it doesnt get better, and check for infections,reactions etc. Hope this helps.