How does histamine affect the bronchial tubes in the lungs during an allergic reaction?
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antihistamine
Antihistamines such as Benadryl (diphenhydramine) and Claritin (loratadine) can be purchased without prescriptions. Both of those agents act by blocking H1 receptors. However, whereas Benadryl binds to those receptors in the central nervous system (CNS), causing drowsiness, Claritin does not readily enter the CNS and thus does not normally cause drowsiness.
During an allergic reaction, the immune system's mast cells release excessive amounts of histamine in response to foreign substances known as antigens.21
When this histamine is released, it acts upon the smooth muscle tissues of the lungs, causing the bronchial tubes (air passages) to constrict. This constriction is a primary factor in the respiratory symptoms associated with allergic reactions, such as wheezing and difficulty breathing.21
To manage these symptoms, antihistamines are often utilized to block the binding of histamine to its receptors, thereby providing relief from the effects of the allergic response.21