<s>[INST] Hi Doc,Past week I had sudden rashes at thigh, buttocks, waistlines, back of elbow and sometimes shoulder; that comes out at night, especially after waking up from a sleep, but gone by day and coming at an alarming cycle. Sometimes itchy, mostly not until I touched it. [/INST] "Hi!Welcome to Healthcaremagic. com.I have read your query in detail and do understand your concern. You seem to be suffering from urticaria. It appears in form of sudden wheals and then settles down without leaving a mark.If you find any causative factors- any dietary substance, dust, exertion, etc, try to avoid it. Usually  long term-low dose treatment is required required in form of antihistamines Apply calamine lotion over affected areas.Investigations in urticaria are more often than not, non contributory. It is very difficult to narrow down to one or more causative factors.Hope this helps!Good luck!" </s>