Sounds like you are suffering from a condition called Urticaria. Urticaria is your bodys allergic response to several things around you.
It can be internal problems like infection of throat, teeth, urinary tract, digestive tract etc. It can also be due to external agents like dust, plant allergens, cosmetic products, clothes, food or medicines (like painkillers).
Next Steps
Consult a Dermatologist near you online. If not responding to medications prescribed online you will need blood tests and injections to control it.
Health Tips
Try to find out what you have done on the day of the allergy and previous day to find the cause of the allergy. In some cases you may not be able to find the cause as the allergy can occur spontaneously