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Your hay fever has kicked into high gear again. You've just pulled out of the medicine cabinet your favored antihistamine medication, and wondering how many to take, and when. You should also stop to consider what is going on within your body that you need an antihistamine, and what is that antihistamine doing.

A very basic primer on allergic reactions.
Your body develops allergies by exposure to various substances, the most common allergy being to pollen. People are also allergic to various foods, chemicals, and even to their pets' dander and hair.

All of these substances are what is known as an allergen, a type of antigen. An antigen is any substance that triggers an immune system response.

On the surface of pollen (or any antigen) are little chemical hooks' that bind to antibodies on the surface of various immune system cells that are spread out within your body and blood stream. If you've been exposed often enough, or to a large dose of an antigen, this binding on the surface of the cells triggers an allergic reaction. Generally, the first immune system reaction your body has to an allergen is the release of histamines.

Histamines are your body's chemical warning bell' much like a fire alarm, alerting the immune system that something foreign is trying to invade, and telling it that it needs to prepare to deal with something potentially dangerous. However, as most hay fever sufferers will tell you, this reaction is not always welcome.

The histamine process.
Histamines flush the affected area, as well as move into your blood stream, causing the affected area to swell, closing off the blood supply to that area, and depending on the cells affected, release mucus in an attempt to flush the offending substance out of your body. Even more severe histamine reactions are constriction of the air passages and possible heart arrhythmia.

That is why during hay fever season, the most common time people need antihistamines, that they experience sore and puffy eyes, a runny nose, and in more severe cases, breathing difficulties and asthma.

But for histamines to work, they have to be detected on the surface of the surrounding cells. Histamines are basically a chemical key' of sorts, opening the door to the various reactions described above, telling your body to get ready to fight.

Why antihistamines work.
What antihistamines do is reach the keyhole' meant for the histamines and temporarily insert themselves into the lock, and thereby prevent the histamine from reaching the cells and preventing the body's response.

Fortunately, antihistamines don't stay locked in place, and neither do histamines.

The body flushes histamines (and antihistamines) out of your system on a regular basis. If it did not do this, once a person's hay fever started, they would be in a permanent state of puffy eyes and runny noses, even after the substance to which they were allergic had left their body. If antihistamines took up permanent residence, your body could become open to serious infections, and the alarm would never be raised to fight it off.

Learn more about this author, W Thomas Payne.
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