Abnormal immune system reaction to any over-the-counter, herbal, or prescription medicine is called drug allergy. Based on how severe the allergic reaction is, it can result in skin rashes, hives, itching, swelling, shortness of breath, and fever, or severe life-threatening complications like anaphylaxis.
Penicillin Toxicity - Causes, Symptoms, and Treatment
If you are allergic to Penicillin, you might get hives, trouble breathing, or swelling. Sometimes, it can cause a severe reaction called anaphylaxis.

Sulfa Allergies Versus Sulfite Allergies - Know the Difference
Sulfa and sulfite allergies are often confused in the context of allergies. Though the names sound similar, these allergies have different effects.