The attachment of the histamine to the receptors causes the cells to be "activated," releasing other chemicals that produce the effects that we associate with allergy (for example, sneezing).Fexofenadine blocks one type of receptor for histamine (the H1 receptor) and thus prevents activation of H1 receptor-containing cells by histamine.They do not always completely control the allergic reaction because they do not counteract other chemicals that may be responsible for the symptoms.
This means it has an effect on small blood vessels, resulting in dilated capillaries (redness), and leakage of protein-rich fluid into surrounding skin (swelling).
Histamine affects nearby nerves resulting in itching.
• Extrapyramidal symptoms are the hallmark of first-generation drugs.
• Side effects differ between first- and second-generation antipsychotics.
Histamine is a chemical that is responsible for many of the signs and symptoms of allergic reactions, for example, swelling of the lining of the nose, sneezing, and itchy eyes.