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Signs and symptoms of penicillin allergy often occur within an hour after taking a drug. Less commonly, reactions can occur hours, days or weeks later.

Drug allergy symptoms may include:

  • Skin rash
  • Hives
  • Itching
  • Fever
  • Swelling
  • Shortness of breath
  • Wheezing
  • Runny nose
  • Itchy, watery eyes
  • Anaphylaxis

Anaphylaxis

Anaphylaxis is a rare, life-threatening allergic reaction that causes the widespread dysfunction of body systems. Signs and symptoms of anaphylaxis include:

  • Tightening of the airways and throat, causing trouble breathing
  • Nausea or abdominal cramps
  • Vomiting or diarrhea
  • Dizziness or lightheadedness
  • Weak, rapid pulse
  • Drop in blood pressure
  • Seizures
  • Loss of consciousness

Other conditions resulting from penicillin allergy

Less common penicillin allergy reactions occur days or weeks after exposure to the drug and may persist for some time after you stop taking it. These conditions include:

  • Serum sickness, which may cause fever, joint pain, rash, swelling and nausea
  • Drug-induced anemia, a reduction in red blood cells, which can cause fatigue, irregular heartbeats, shortness of breath and other symptoms
  • Drug reaction with eosinophilia and systemic symptoms (DRESS), which results in rash, high white blood cell counts, general swelling, swollen lymph nodes and recurrence of dormant hepatitis infection
  • Inflammation in the kidneys (nephritis), which can cause fever, blood in the urine, general swelling, confusion and other symptoms

When to see a doctor

See your doctor as soon as possible if you experience signs or symptoms of penicillin allergy.

Call 911 if you experience signs of a severe reaction or suspected anaphylaxis after taking penicillin.

Nov. 22, 2014

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