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Medical Author:

Samuel M. Keim, MD

Samuel M. Keim, MD

Dr. Keim received a Bachelor of Science degree from Northern Arizona University, where he studied Microbiology, Chemistry and Spanish. After graduating from The University of Arizona College of Medicine, he completed a residency in Emergency Medicine at Los Angeles County King Drew Medical Center.

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Medical Editor:

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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An allergic reaction is caused by the body's immune system overreacting to the drug, which is viewed as a chemical "invader," or antigen. This overreaction is often called a hypersensitivity reaction.

• The body produces antibodies to the antigen and stores the antibodies on special cells.
  • The antibody in an allergic reaction is called immunoglobulin E, or IgE.
    
    
  • When the body is exposed to the drug again, the antibodies signal the cells to release chemicals called "mediators." Histamine is an example of a mediator.
    
    
  • The effects of these mediators on organs and other cells cause the symptoms of the reaction.

• The most common triggers of drug allergies are the following:
  • Painkillers (called analgesics) such as codeine, morphine, nonsteroidal antiinflammatory drugs (NSAIDs, such as ibuprofen or indomethacin), and aspirin
    
    
  • Antibiotics such as penicillin, sulfa drugs, and tetracycline
    
    
  • Antiseizure medications such as phenytoin (Dilantin) or carbamazepine (Tegretol)

• Risk factors for drug allergies include the following:
  
  
  • Frequent exposure to the drug
    
    
  • Large doses of the drug
    
    
  • Drug given by injection rather than pill
    
    
  • Family tendency to develop allergies andasthma
    
    
  • Certain food allergies such as to eggs, soybeans, or shellfish

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