It isn't clear why some people develop penicillin allergies, while others don't. However, certain people seem to be at greater risk of developing a penicillin allergy than others are.

You may be at higher risk if:

  • You're between the ages of 20 and 49
  • You've taken penicillin frequently
  • You have HIV/AIDS
  • You have cystic fibrosis
  • You've had allergic reactions to penicillin or another drug in the past
Dec. 15, 2011

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