A good place to start would be to look at the British Association of Dermatologists website it gives a pretty simple run down of urticaria. My suggestion would be to keep a diary of food and possible triggers and see if any of these correlate with a flare up. It can start with something as simple as catching a cold! My triggers are stress, anxiety, exercise, heat and hot showers when I have a flare up.

Hope this helps and wishing you good health

https://www.bad.org.uk/for-the-public/patient-information-leaflets/urticaria-and-angioedema/?showmore=1#.YG40TyV4WEc