Hi,
When you have an allergic reaction to a substance, histamine and other chemicals are released into your bloodstream, causing itching, swelling, and other symptoms.
Many substances can trigger hives:
Medications
Shellfish, fish, nuts, eggs, milk, and other foods
Pollen
If you have noticed these symptoms specifically after taking a particular drug then one of them could be the cause.
You cannot discontinue all medications and try to figure out which one it is, which is usually the way the trigger substance is identified.
You can take anti-histamines to trreat this and apply Calamine lotion on the affected areas.
You could meet with an allergist and and discuss what options you have regarding this issue.
ref:http://www.myonlinewellness.com/topic/adam1000845