Antihistamines for Hay Fever


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For many people, one way to battle the dreaded symptoms of hay fever each year is to take antihistamines.

When the body’s immune system comes into contact with any of a variety of pollens that circulate in the air during the hay fever season, a very specific reaction begins to take place. The large amounts of histamines that are generated in mast cells are prompted for release into the circulatory system. They seek out and attach themselves to special receptors called H1 receptors. These are found on lots of different cells. Once histamines are bound to these receptors it causes the vessels in the area in which they bind to become dilated and more easily penetrable by other specialised cells that are then mobilised to combat the allergic response. Histamines will tend to amass in the eye, nose and throat area where the pollens will first come in to contact, and this is what causes the typical hay fever symptoms such as the itching, runny eyes and nose and sneezing. By blocking the ability of the histamines to bind with the H1 receptors, antihistamines are able to greatly decrease the symptoms caused by an allergic response during the hay fever season.

First Generation Antihistamines

There are basically two different types of antihistamines. When they were first introduced to the market (called first generation antihistamines) they had a sedative effect in addition to the antihistamine properties. Taking them tended to make you sleepy. Although this was useful at night times when itching might make sleep more difficult, during the day it was of little use unless you were able to accommodate the drowsiness.

Second Generation Antihistamines

The second type of antihistamine (called second generation antihistamines) were developed to be non- drowsy and had lasting effects without any sleepiness. That vast majority of antihistamines on the market today are the non-drowsy types.

Administration of Antihistamines

Antihistamines can come in a variety of different mediums. For hay fever relief, they are usually taken as pills or capsules, liquids, drops for the eyes and nose, sprays for nasal inhalation and injections. Depending on the severity of the symptoms, many antihistamines can be bought over the counter. If symptoms are more severe, your GP can prescribe something stronger, or even recommend a course of injections.

Side Effects of Antihistamines

The more common side effects of taking antihistamines are drowsiness (first generation) and dry mouth. In some instances, although not very common, feelings of an upset stomach or a headache can occur. If this should happen then stop taking the antihistamine. If it persists even after you stop taking it then it is probably best to see your GP.

Most of the different types of antihistamine will work for either a period of 12 / 24 hours at a time. This depends entirely on the product you should choose and how you best want to manage your symptoms. If you are taking any other medications it is always best to check first with your GP just to make sure that there will not be any negative interaction between the two different medications. Sometimes taking other medications will cause the antihistamine to become less effective in relieving the symptoms of an allergic attack.


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Guide to Hay Fever