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5 Facts about Antihistamines

Anti-histamines are life savers for almost everyone. Around 1 in 4 people in Britain suffer from allergies and most of the world’s population tackle hay fever every spring & summer and others have all year round rhinitis causing sneezing, watery eyes, itching and rashes.

Fact number 1: Anti-histamines block the action of histamine in the body. Histamine is the compound that is released during the allergic reaction at H1 receptor sites, which induces symptoms of hay fever, allergic rhinitis, allergic skin conditions or allergic conjunctivitis (inflammation of the eyes).

Fact number 2: Anti-histamines have a useful side effect of being able to prevent nausea and vomiting and sedation.

Fact number 3: There are 1st, 2nd and 3rd generation antihistamines:

 • 1st generation antihistamines, such as diphenhydramine and chlorphenamine, which can induce symptoms of drowsiness

 • 2nd generation antihistamines, such as loratadine and cetirizine, a drowsiness-free and are usually the most recommended antihistamine drug
 • 3rd generation antihistamines, such as levocetirizine and fexofenadine, have been altered to be able to have less serious side effects than the 2nd generation drug side effects

Fact number 4: Anti-histamines can be given in eye drops, Lodoxamine trometamol as an example. Some people might have extra sensitivity of pollen, grass, animal hair or even house dust, which cause red and itchy eyes. Anti-histamine eye drops are able to relieve the symptoms.

Fact number 5: Some antihistamine drugs have useful side effects as well as blocking histamine.

Chlorpromazine is an anticholinergic drug primarily, it also blocks histamine receptors and also has even been proven to prevent surgical shock. 
[1]Encyclopedia: Antihistamine 
[2]NHS Antihistamines 
[3]Web MD antihistamines
[4]NHS Eye Antihistamines
[5]An introduction to Medicinal Chemistry, G. L. Patrick- Book

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