It is possible that you are having infection-related urticaria
(urticaria is red itchy weals that come and go; triggers: infection, stress
, autoimmunity and most are spontaneous).
You will need a complete blood count
, CRP, LFTs, urine c/s, stool c/s (if still having abdominal pains) to exclude an infection.
Appropriate antibiotics and long-acting antihistamines such as fexofenadine
180mg once daily for a week is required to control this. Sometimes you may need to continue on the antihistamines for longer.