This does seem to be an allergic reaction which is manifesting as rash
/hives. Hives are raised, often itchy, red welts on the surface of the skin.
When you have an allergic reaction to a substance, histamine and other chemicals are released into your bloodstream, causing itching, swelling, and other symptoms. The common triggers are medications, foods (shellfish, fish, nuts, eggs, milk, and other foods), pollen and insect bites.