Signs and symptoms of a drug 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
- Shortness of breath
- Runny nose
- Itchy, watery eyes
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
- 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 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 drug allergy.
Call 911 if you experience signs of a severe reaction or suspected anaphylaxis after taking a medication.
Oct. 10, 2014
- Joint Task Force on Practice Parameter. Drug allergy: An updated practice parameter. Annals of Allergy, Asthma & Immunology. 2010;105:259.
- Drug reactions and drug allergies. American College of Allergy, Asthma & Immunology. http://www.acaai.org/allergist/ALLERGIES/TYPES/DRUG-ALLERGY/Pages/default.aspx. Accessed July 22, 2014.
- Drug hypersensitivity. The Merck Manual for Health Care Professionals. http://www.merckmanuals.com/professional/immunology_allergic_disorders/allergic_autoimmune_and_other_hypersensitivity_disorders/drug_hypersensitivity.html?qt=drug sensitivity&alt=sh. Accessed July 22, 2014.
- Chiriac AM, et al. Drug allergy diagnosis. Immunology and Allergy Clinics of North America. 2014;34:461.
- Romano A, et al. Antibiotic allergy. Immunology and Allergy Clinics of North America. 2014;34:489.
- Anaphylaxis. The Merck Manual for Health Care Professionals. http://www.merckmanuals.com/professional/immunology_allergic_disorders/allergic_autoimmune_and_other_hypersensitivity_disorders/anaphylaxis.html?qt=anaphylaxis&alt=sh. Accessed Aug. 10, 2014.
- Adkinson NF, et al. Middleton's Allergy: Principals and Practice. 8th ed. Philadelphia, Pa.: Saunders Elsevier; 2014. http://www.clinicalkey.com. Accessed July 22, 2014.
- Young JS, et al. Chemotherapeutic medications and their emergent complications. Emergency Medicine Clinics of North America. 2014;32:563.