From the Research
Yes, it is possible to be allergic to antihistamines, though it's relatively rare. Allergic reactions can occur to any medication, including those designed to treat allergies. Common antihistamines like diphenhydramine (Benadryl), cetirizine (Zyrtec), loratadine (Claritin), and fexofenadine (Allegra) can trigger allergic responses in sensitive individuals. Symptoms of an antihistamine allergy may include hives, rash, itching, swelling (especially of the face, lips, tongue, or throat), difficulty breathing, or anaphylaxis in severe cases. If you suspect you're allergic to an antihistamine, stop taking it immediately and consult a healthcare provider. They may recommend allergy testing or suggest alternative medications from a different chemical class. This paradoxical reaction occurs because antihistamines contain inactive ingredients like dyes, preservatives, or fillers that can trigger allergies, or in rare cases, the active ingredient itself may cause a reaction through immune system mechanisms different from those involved in the conditions antihistamines typically treat.
Key Points to Consider
- The most recent and highest quality study on the topic is from 2023, which discusses the evidence-based use of antihistamines for treatment of allergic conditions 1.
- Antihistamines can cause hypersensitivity reactions, including anaphylaxis, urticaria, and contact dermatitis, as reported in a study from 2013 2.
- The incidence of anaphylaxis, a life-threatening systemic reaction, is 2.1 per 1,000 person-years, and medications are one of the most common triggers, as stated in a study from 2020 3.
- Symptoms of an antihistamine allergy can be similar to the disease being treated, making diagnosis challenging, and may require challenge testing or alternative medications, as discussed in a study from 2013 2.
Recommendations for Clinical Practice
- Be aware of the potential for antihistamine allergy and monitor patients for signs of hypersensitivity reactions.
- Consider alternative medications or formulations if a patient experiences an allergic reaction to an antihistamine.
- Follow the most recent guidelines and evidence-based recommendations for the use of antihistamines in the treatment of allergic conditions, as outlined in a study from 2023 1.