Do oral antihistamines have side effects?

Dr. Jeanne Morrison, PhD
Family Practitioner

Oral antihistamines can help relieve environmental allergies, but like all drugs, they can have side effects. Certain antihistamines can make you very drowsy. Some antihistamines should not be given to children or older people. Unless you know how you will react, do not use antihistamines while driving or using heavy machinery. Check with your doctor to see if these medications are right for you.

Dr. Daniel R. Spogen, MD
Family Practitioner

Oral antihistamines have side effects, including dry mouth and tiredness. The most commonly used second generation antihistamines such as loratidine (Claritin ), cetirizine (Zyrtec), and fexofenadine (Allegra) can all cause dry mouth and tiredness although they are less sedating than older first generation antihistamines such as Benadryl. These side effects happen especially when higher doses than recommended are taken. Oral antihistamines are also available combined with a decongestant, most commonly pseudoephedrine. Decongestants can cause many side effects such as increased blood pressure and heart rate, tremors, insomnia, dizziness, and increased eye pressures in people with glaucoma.

Donna Hill Howes, RN
Family Practitioner

Side effects may include abdominal pain, loss of appetite, nausea, vomiting, diarrhea, and constipation. Other side effects include dry mouth, nose, or throat, vision problems, ringing in the ears, drowsiness, dizziness, vertigo (a spinning sensation), insomnia, tremor, nervousness, irritability, and weakness. Some people have trouble emptying the bladder. Men may have erection problems. 

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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.