Any medication, including over-the-counter, can cause a reaction in the right person. The appearance can vary widely from hives to blisters to a red rash. Often the rash will occur within one to two weeks of starting the medication. A common drug reaction is hives (urticaria). More severe cases can cause angioedema which is swelling of the skin often on the lips or hands.
A different and more severe drug reaction is called erythema multiforme.
Typically it consists of numerous red to purple target-shaped lesions on the skin of the body and extremities and characteristically on the palms of the hands and soles of the feet.
Treatment: anti-itch lotions and antihistamine pills (over-the-counter) and steroid creams and cortiosteroids (prescription) as well as identifying and eliminating the offending medication