How Do antihistamines work for allergic rhinitis and other allergy symptoms?
Before we talk about ANTI-histmamines, we should talk about how histamines are involved in allergic reactions. Then we can talk about how ANTI-histamines work.
The typical symptoms that are listed as acute allergy symptoms include sneezing, nasal irritation, runny nose, scratchy throat, and itchy eyes. These are the irritative symptoms or “histamine-related symptoms” that occur in the typical case of allergic rhinitis. They are easy to identify in most cases because they come on suddenly and in a recognizable pattern after exposure to a particular airborne particles, called an allergen. In fact, they come on so suddenly that they are called the acute symptoms of allergic rhinitis. Scientists have studied this allergic reaction and understand precisely what is occurring in this typical acute allergic response. The allergen is absorbed into the mucus where it binds to particular antibodies on the surface of cells called Mast cells. You don’t need to remember the names of these cells. I’ve put it here for those that are particularly curious. When the allergen, antibody, mast cell interaction occurs, it triggers a cascade of chemical events in the nasal tissues (and elsewhere) which cause these allergy symptoms. An important part of this cascade of chemical events is the release of a particular chemical called histamine. Histamine is responsible for the irritative symptoms that occur in the nose, eyes, throat, and elsewhere. Many decades ago, scientists discovered a class of drugs called the antihistamines that block the effect of histamines and stopped or greatly diminished these irritative effects of the typical allergic reaction. Patients and doctors have enjoyed the benefits of prescribing taking these medications. They provide excellent relief to these irritative symptoms.
Many patients need nothing more than over-the-counter antihistamine medications or prescription antihistamines to relieve their symptoms. Others find only partial relief with antihistamines. Here’s why. Antihistamines only treat part of the chemical cascade that occurs with allergy attack. Antihistamines block the histamine portion of the allergic response, but there is a second part of the response, called chronic inflammation. And a fair number of allergy sufferers experience this chronic inflammation that occurs with allergic rhinitis and don’t get all the relief that is possible if they are using antihistamines alone.
The chronic component to allergic rhinits is in an upcoming blog.
In the meantime, here is a nice video on how allergies cause histamine release.
See also my Top 10 facts about allergies
Jeffrey E. Terrell, MD
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