hi and welcome to HCM The first thing to rule out would be an allergic reaction, probably to something you didnt notice. It could be sun exposure, outdoor activity, plants, pets, presence of mites or bugs, etc. Also if you have had fever or such symptoms it may be a viral infection. I would advise you to use a calamine based lotion on the bumps twice a day and an antihistamine tablet at night for a week,like levocet etc., and look for changes. Allergies should improve with this. keep a note if other family members, contacts have similar complaints to rule out mites or parasite infection, in which case all need simultaneous treatment to prevent further spread. If the bumps persist or keep coming back, do consult a dermatologist who can examine you and rule out these conditions and advise blood and skin tests as necessary. hope this helps.