Hello,
What you seem to be having is hives. Hives can appear as a side effect of medicines. You can apply an anti-itch cream or lotion to the affected area. Oral antihistamine, such as Benadryl can also be used. You should take a comfortably cool bath and wear smooth-textured cotton clothing. You should choose mild soaps without dyes or perfumes and use a mild, unscented laundry detergent when washing clothes, towels and bedding.
Please take a second opinion from a dermatologist if the symptoms persist. He/She will start with the specific medications like steroids. Also consult your doctor for the dose of anti coagulants.
I hope it helps. Take care and please do keep me posted in case you have any additional doubts. Kind regards.