Hello,
It looks like hives or urticaria to me. You can apply some calamine lotion at the rash as it will help in soothing the skin. You can take some OTC oral antihistamine medications like Benadryl or Claritin and also apply steroid cream on the rash. If still the symptoms do not improve then please get a clinical examination done by a dermatologist.
I hope it helps. Take care and regards.
It could be you're having an allergic reaction to soaps and detergents or even a food intolerance or something like this. Or, if something is biting you, you are allergic, to the welts spread. I thought of the detergents and soaps, because this is a common allergen for people to suddenly become allergic to and allergies do act differently in some people.
I would actually recommend getting a referal to see an allergist. Insurance companies require referals, as do the allergists themselves. Get an extensive panel. Test for the things you suspect in particular.
In the mean time, until about a week or two before the appointment, try using oral Benadryl at the prescription dosage, which is 50 mg every 8 hours. It will make you drowsy, but if this is an allergy, it should help some.
I recommend also testing for Histamine Intolerance. Please go to mercola.com and see his videos about Histamine Intolerance. There is more to this than a simple blood test for Histamine Intolerance. Do other research about Histamine Intolerance, too. He is a very good resource, though.