Antihistamines for allergies


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Antihistamines for allergies


Allergy medications

Antihistamines for allergies

Asthma and COPD medications

Bronchodilators: Beta 2-agonists and muscarinic antagonists

Bronchodilators: Leukotriene antagonists and methylxanthines

Pulmonary corticosteroids and mast cell inhibitors


Antihistamines for allergies


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Antihistamines for allergies

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Cetirizine p. 710


Content Reviewers

Yifan Xiao, MD


Jung Hee Lee, MScBMC

Filip Vasiljević, MD

Evan Debevec-McKenney

Salma Ladhani, MD

Antihistamines for allergies, also known as H1 blockers, are medications that are primarily used to treat allergic reactions, such as urticaria, angioedema, and allergic rhinitis.

These conditions are related to an increased release of histamine.

Now, H1 blockers work by blocking the effects of histamine in tissues that have H1 receptors, thereby alleviating symptoms of allergic reactions.

In order to understand how antihistamines work, first we need to talk briefly about histamine and allergic reactions.

Histamine is a small molecule that’s mainly produced by mast cells and basophils.

Once released, they cause local inflammation and vasodilation. However, they are also present in the brain as neurotransmitters, and they are produced by enterochromaffin cells in the stomach to increase gastric acid secretion.

Okay, so in order to develop an allergic reaction, an allergen, say pollen, needs to enter the body and cause the activation of B cells.

Activated B-cells produce IgE antibodies that get released into the bloodstream and bind to mast cells.

The mast cells are now “primed,” meaning that if pollen enters the body again in the future, the mast cells degranulate and release their histamine into the local tissue.


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  5. "The Role of Histamine in the Pathophysiology of Asthma and the Clinical Efficacy of Antihistamines in Asthma Therapy" International Journal of Molecular Sciences (2019)
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