Symptoms

Signs and symptoms of a serious drug allergy often occur within an hour after taking a drug. Other reactions, particularly rashes, can occur hours, days or weeks later.

Drug allergy signs and symptoms may include:

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

Anaphylaxis

Anaphylaxis is a rare, life-threatening reaction to a drug allergy 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
• Seizure
• Loss of consciousness

Other conditions resulting from drug allergy

Less common drug allergy reactions occur days or weeks after exposure to a drug and may persist for some time after you stop taking the drug. 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 rash with eosinophilia and systemic symptoms (DRESS), which results in rash, high white blood cell count, 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

Call 911 or emergency medical help if you experience signs of a severe reaction or suspected anaphylaxis after taking a medication.

If you have milder symptoms of a drug allergy, see your doctor as soon as possible.