Allergen Fact Sheets

Drug Allergy Allergen Facts, Symptoms, and Treatment

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Drug Allergy

Adverse drug reactions (ADRs) are any harmful or unintended reaction to a drug that occurs at doses used for prevention, diagnosis, or treatment. They’re classified as either predictable reactions that may occur in anyone (Type A) or unpredictable reactions that occur in only susceptible individuals (Type B). Predictable reactions (Type A) (e.g., side effects, overdoses, and drug interactions) are the most common type of ADRs. Unpredictable reactions (Type B) occur in approximately 20 to 25 percent of patients who experience ADRs; these reactions are generally unrelated to the pharmacologic actions of the drug.1

A drug allergy, then, is one type of unpredictable (Type B) ADR, and it accounts for approximately 5 to 10 percent of all ADRs.1 To put it another way, a drug allergy is an abnormal immune-system reaction to a drug, be it prescription, over the counter, or herbal. Drug-allergy reactions can happen the first time the medication is taken or only after repeated exposure.2

Risk factors associated with developing a drug allergy include age (they’re more common in young/middle-aged adults), gender (they’re less common in men than women), presence of genetic polymorphisms and/or viral infections (e.g., HIV, herpes), previous drug reactions, and drug-related factors (e.g., the method of administration, single versus frequent dosing).1

What are some common medications that cause drug allergies?

Any drug can cause an allergic reaction, but some of the most common medications causing drug allergies include:1,2

  • Penicillin
  • Sulfonamides
  • Cephalosporins
  • Radiocontrast media (RCM)
  • Local anesthetics (e.g., Novocain, lidocaine)
  • General anesthetics
  • Acetylsalicylic acid/NSAIDs

Analgesics (aka pain killers) and antibiotics are the drug classes most commonly implicated in drug allergy and drug-induced anaphylaxis, but regional variations have been observed.4

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Are there other allergens I could be sensitized to?*

Drug-allergy reactions can occur regardless of whether the drug is administered in liquid, pill, or injectable form.5 In addition, some drugs are cross-reactive.1 For example, in the case of allergy to β-lactam antibiotics, cross-reactions to penicillin, ampicillin, and amoxicillin are possible.3

How do I manage my allergy?

Your healthcare provider may recommend a plan that includes the following.1,2,6

  • Avoid or discontinue the offending drug.
  • Substitute alternative medications with unrelated chemical structures if possible. However, consider any cross-reactivity when choosing substitutions.
  • Inform healthcare workers (including specialists and dentists) of your allergy and ensure it’s clearly noted in your medical records.
  • Ask your doctor for a list of drugs (including over-the-counter medications) to avoid.
  • Consider wearing a medical-allergy bracelet or necklace to notify others of your condition, particularly if you have a history of severe reactions.

Your healthcare provider may direct you to take one of the following medications to improve your allergy symptoms:

  • Employ topical corticosteroids and oral antihistamines to potentially improve skin-related symptoms.

If someone you’re with is having an allergic reaction and showing signs of shock, act quickly. Look for a weak, rapid pulse; trouble breathing; cool, clammy, and pale skin; confusion; and loss of consciousness. Immediately do the following: 

  • Call local emergency services.
  • Ensure the affected individual is lying down with legs elevated.
  • Administer epinephrine or adrenaline immediately (if available) for any obvious signs of anaphylaxis.
  • Check the affected individual's pulse and breathing and administer CPR or other first-aid measures if necessary.

Looking for more allergy info and management tips?

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Common Symptoms

Drug-allergy reactions most frequently and prominently affect the skin.1 In fact, allergic maculopapular rash, which often resembles measles or rubella, comprises an estimated 75 percent of all such reactions. However, responses also can manifest as organ or systemic reactions, such as serum sickness, various types of rash with eosinophilia and systemic symptoms (DRESS, drug rash with eosinophilia and systemic symptoms), and anaphylaxis.3

Symptoms of drug allergy can include:2

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

Drug allergy can also cause anaphylaxis, which can include symptoms such as:2

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

The following conditions and their related symptoms also can occur days or weeks after exposure and can persist after you stop taking the offending drug.2

  • Serum Sickness: fever, joint pain, rash, swelling, nausea
  • Anemia: fatigue, irregular heartbeats, shortness of breath, etc.
  • Drug rash with eosinophilia and systemic symptoms (DRESS): rash, high white blood cell count, swelling, recurrence of dormant hepatitis infection, swollen lymph nodes
  •  Kidney inflammation: fever, swelling, confusion, blood in urine, etc.

Given the plethora of symptoms associated with drug allergy, diagnosis is particularly challenging.1

How do I know if I'm allergic?*

Together with your symptom history, specific IgE blood testing can help determine if you are sensitized to a particular allergen. If you are diagnosed with an allergy, your healthcare provider will work with you to create a management plan.

*These products may not be approved for clinical use in your country. Please work with your healthcare provider to understand availability.

Is there a risk for a severe event?

Drug allergy can cause anaphylactic reactions, although this response is quite rare.3 That said, drugs account for 58.8 percent of all anaphylaxis-related death in the United States.4 Anaphylaxis is most commonly observed after administration of nonsteroidal anti-inflammatory agents, intravenous contrast agents, aspirin, and β-lactam antibiotics.3

  1. Warrington R, Silviu-Dan F. Drug allergy. Allergy Asthma Clin Immunol. 2011 Nov 10;7(Suppl 1):S10. Available from:
  2. Mayo Clinic [Internet]. Rochester, MN: Mayo Foundation for Medical Education and Research; 2020 Oct 15. Available from:
  3. Żukiewicz-Sobczak WA, Wróblewska P, Adamczuk P, Zwoliński J, Oniszczuk A, Wojtyła-Buciora P, Silny W. Drugs as important factors causing allergies. Postepy Dermatol Alergol. 2015 Oct;32(5):388-92. Available from:
  4. Regateiro F, S, Marques M, L, Gomes E, R: Drug-Induced Anaphylaxis: An Update on Epidemiology and Risk Factors. Int Arch Allergy Immunol 2020;181:481-487. doi: 10.1159/000507445. Available from: 
  5. American College of Allergy, Asthma & Immunology [Internet]. Arlington Heights, IL: American College of Allergy, Asthma & Immunology; 2018 Feb 28. Available from:
  6. Mayo Clinic [Internet]. Rochester, MN: Mayo Foundation for Medical Education and Research; 2019 Sep 14. Available from: