How antihistamines work: allergy relief explained

Healthylife Pharmacy20 December 2013|3 min read

The primary use of antihistamines is to control the symptoms of conditions associated with allergic reactions. They are not cures for such conditions but may provide relief from pain, itchiness and discomfort resulting from symptoms. Conditions on which antihistamines may help include urticaria (also known as nettle rash or hives), allergic rhinitis (inflammation of the nasal passage commonly associated with hay fever), insect bites or stings, allergic conjunctivitis (inflammation of the eyes) and mild allergic reactions caused by particular foods.

How do antihistamines work?

It is the function of antihistamines to inhibit the action of histamine by targeting histamine receptors in cells. Histamine is a chemical that forms part of the body’s immune system and helps protect the body’s cells against infection. When the immune system detects a potentially harmful bacteria or virus, histamine is released into cells, causing blood vessels to expand and skin to swell. This inflammation may often lead to skin becoming red and swollen, resulting in itchiness. It also causes fluid to escape from capillaries into tissues, often manifesting as a runny nose and watery eyes during allergic reactions.

As antagonists, the purpose of antihistamines is to prevent the binding of histamine to receptors in the endothelium (the thin layer of cells lining the interior surface of blood and lymphatic vessels), nerves, vascular smooth muscle (which composes the majority of the walls in blood vessels), glandular cells and mast cells (a key part of the body’s immune system).

H3: Antihistamine receptors

There are four separate histamine receptors in each of the body’s cells:

H1- receptor causes inflammation

H2- receptor aids in the stimulation and production of stomach acids

H3- receptor is understood to help stimulate chemical reactions that help transmit information around the brain

H4- receptor is not currently well understood but is considered to play a role in the regulation of the immune system.

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References

  1. https://www.healthdirect.gov.au/antihistamines 
  2. Farzam, K., & O’Rourke, M. C. (2022, December 27). Antihistamines. PubMed; StatPearls Publishing.https://www.ncbi.nlm.nih.gov/books/NBK538188/ 
  3. Randall, K. L., & Hawkins, C. A. (2018). Antihistamines and allergy. Australian Prescriber, 41(2), 42–45. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5895478/
  4. Gómez, R. M., Moreno, P., Compalati, E., Canonica, G. W., & Ansotegui Zubeldia, I. J. (2023). Update meta-analysis on the efficacy and safety issues of fexofenadine. World Allergy Organization Journal, 16(7), 100795. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10401337/
  5. Hon, K. L., Leung, A. K. C., Ng, W. G. G., & Loo, S. K. (2019). Chronic Urticaria: An Overview of Treatment and Recent Patents. Recent Patents on Inflammation & Allergy Drug Discovery, 13(1), 27–37. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751347/ 
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This article is for informational purposes only and does not provide medical advice, diagnosis, or treatment. Any information published on this website or by this brand is not intended as a substitute for medical advice. If you have any concerns or questions about your health you should consult with a health professional.