Tolerance to the sedative effects of antihistamines can develop quickly.
As a result, the longer you take them, the less likely they are to make you sleepy.
There are two kinds of histamine receptors, H1 and H2.
These receptors both receive histamine as a messenger, but the meaning conveyed is different.
Diphenhydramine and doxylamine have anticholinergic properties that make them poor choices for older adults.
Recent studies have shown that anticholinergics may increase the risk of dementia.
There's not much evidence to suggest any particular antihistamine is better than any other at relieving allergy symptoms.
Antihistamines are inhibitors of histamine receptors. H1-antihistamines, inhibit competitively H1 receptors and the corresponding effects i. They do not inhibit antigen/antibodies reactions, nor histamine release, they inhibit H1 effects.
H1-antihistamines have been used for more than fifty years in treating various allergic manifestations. H1-antihistamines which penetrate into brain elicit, by inhibiting stimulant effect of histamine, drowsiness.
Most antihistamines can be bought from pharmacies and shops, but some are only available on prescription.
This page covers: Types of antihistamines How to take them Side effects Taking them with other medicines, food or alcohol Who can take them – including pregnancy advice How they work There are many types of antihistamine.
Skin sensations local itching or burning sensation, flushing and a disagreeable heat.