What should I know before taking oral antihistamines?

Before taking oral antihistamines you should know that generally the second generation second generation antihistamines such as loratidine (Claritin), cetirizine (Zyrtec) and fexofenadine (Allegra) are safe as long as they are taken at the recommended doses. You should avoid those that are combined with decongestants such as pseudoephedrine if you have a history of high blood pressure, heart disease, glaucoma, or insomnia. You should also stop taking decongestants if you experience side effects such as increased blood pressure, heart rate, tremors, or dizziness. If your allergy symptoms are more persistent and bothersome, you should consider using a daily steroid nasal spray as this is considered first line treatment for patients whose allergies are affecting their quality of life.

Donna Hill Howes, RN
Family Practitioner

If you have seizures, an enlarged prostate (BPH), bladder neck obstruction, cardiovascular disease, chronic obstructive pulmonary disease (COPD), angle-closure glaucoma, high blood pressure, or hyperthyroidism, an oral antihistamine may not be a good option for you.

Oral antihistamines may not be a good option for women who are pregnant, may be pregnant, or are planning pregnancy. It is not known if they are safe for pregnant women.

You should not take oral antihistamines if you are breastfeeding.

If you take fexofenadine, you should avoid apple, grapefruit, and orange juice. 

This answer was adapted from Sharecare's award-winning AskMD app. Start a consultation now to find out what's causing your symptoms, learn how to manage a condition, or find a doctor.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.