Watery eyes, runny nose, itchy throat, sneezing, hives...all thanks to our body trying to defend us. Our immune system is continually at work protecting us from being bombarded by disease causing microbes. We stay healthy for the most part because we are protected from infection. Unfortunately often times we are exposed to relatively harmless materials, such as allergens, but because our bodies respond to rid themselves of any uncommon attacker, we have the above symptoms. When our bodies recognize they are being invaded by something foreign, one of their responses is to produce a substance called histamine. Mast cells (fixed location) and basophils (free floating cells) bind to the allergens and produce this histamine, along with an antibody known as immunoglobulin E. The production of these substances dilates blood vessels, promotes proteins to be released from cells and allows for increased blood flow to the point of invasion. Along with increase in blood flow comes an increase in mucous production, hence the watery eyes and runny nose.

Once we are steeped in the misery of our bodies reacting to allergens, we often reach for antihistamines literally "against histamine." We know that this medication will provide us with relief from the itchy, watery, runny and sneezy body parts. But how do antihistamines work? Considering cells have a limited number of attachment points, antihistamines look to bind to the receptor sites and effectively block the histamine from binding. As mentioned earlier, the histamines ultimately cause an increase in mucous production which it cannot do if it cannot bind with the cell.

Histamines actually have an upside to them as they work to keep us alert and awake. Since we reach for antihistamines when we feel bad, we effectively block all histamines, not just the ones involved with allergic reactions. One of the side effects of the over the counter' version of antihistamines is marked drowsiness. By blocking the receptors in the brain, our ability to stay awake becomes impaired. As much as we enjoy being allergy symptom free, being less attentive and drowsy does not work too well in society. Fortunately there are prescription antihistamines which are not absorbed by the brain, so this sleepy effect usually does not take place.

Antihistamines must be taken early on when a reaction begins to occur. Once the histamines have bound themselves to the cells, they cannot be removed. Taking antihistamines with all cells bound would serve no purpose except to make you less alert. So again we reach for a medicinal aid, in this case a decongestant. These work to reduce congestion by contracting the blood vessels and diminishing mucous production. Where antihistamines make us drowsy, decongestants often make us jittery. So often times the makers of pharmaceuticals will blend an antihistamine and decongestant in order to counteract the side effects.

The best advice if taking the sedating antihistamines would be to take it at bedtime to prevent daytime drowsiness. Visiting your physician to receive the prescription version of the antihistamines would be recommended to help with daytime symptoms.

Learn more about this author, CD Gozzi.
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