Allergic rhinitis - antihistamine; Hives - antihistamine; Allergic conjunctivitis - antihistamine; Urticaria - antihistamine; Dermatitis - antihistamine; Eczema - antihistamine
An allergy is an immune response, or reaction, to substances (allergens) that are usually not harmful. In someone with allergies, the immune response is oversensitive. When it recognizes an allergen, the immune system launches a response. Chemicals such as histamines are released. These chemicals cause allergy symptoms.
One type of medicine that helps relieve allergy symptoms is an antihistamine.
Antihistamines are medicines that treat allergy symptoms by blocking the effects of histamine. Antihistamines come as pills, chewable tablets, capsules, liquids, nasal sprays, and eye drops. There are also injectable forms used mainly in health care settings.
Antihistamines treat these allergy symptoms:
Treating symptoms can help you or your child to feel better during the day and sleep better at night.
Depending on your symptoms, you can take antihistamines:
For many people with allergies, symptoms are the worst around 4 a.m. to 6 a.m. Taking an antihistamine at bedtime may help you or your child feel better in the morning during allergy season.
You can buy many different brands and forms of antihistamines without a prescription.
Ask your health care provider what type of antihistamine and what exact dosage is right for you or your child. Make sure you understand how much to use and how many times a day to use it. Be sure to read the label carefully. Or ask your pharmacist if you have questions.
Ask your provider if antihistamines are safe for you or your child, what side effects to watch for, and how antihistamines may affect other medicines you or your child take.
There may be special precautions for using antihistamines if you have:
Side effects of antihistamines may include:
Call your provider if:
Corren J, Baroody FM, Togias A. Allergic and nonallergic rhinitis. In: Burks AW, Holgate ST, O'Hehir RE, et al, eds. Middleton's Allergy: Principles and Practice. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 40.
Seidman MD, Gurgel RK, Lin SY, et al. Clinical practice guideline: allergic rhinitis. Otolaryngol Head Neck Surg. 2015;152(1 Suppl):S1-S43. PMID: 25644617 pubmed.ncbi.nlm.nih.gov/25644617/.
Wallace DV, Dykewicz MS, Oppenheimer J, Portnoy JM, Lang DM. Pharmacologic treatment of seasonal allergic rhinitis: synopsis of guidance from the 2017 joint task force on practice parameters. Ann Intern Med. 2017;167(12):876-881. PMID: 29181536 pubmed.ncbi.nlm.nih.gov/29181536/.BACK TO TOP
Review Date: 4/10/2022
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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