Hay Fever Site

As the name suggests, antihistamine works to combat the release of histamine – the natural chemical discharged by the body during an allergic reaction which is involved in creating inflammation. This drug is a manufactured chemical that is so similar to natural histamine that the mast cells in the lining of the nose, mouth and eyes are fooled into believing it is real and so accept its presence. However, it is not identical, as it would then provoke the cells to cause allergy symptoms. Therefore, antihistamine effectively blocks many of the body’s histamine receptors, preventing them from producing the symptoms of an allergic reaction. Antihistamine is a basic treatment of urticaria (also called hives or nettle rash) as well as hay fever. It used to be employed as a treatment for asthma, too, but now in Western soci­eties there are many more sophisticated asthma medications.

There is a problem with using antihistamine to stop the release of histamine in the body: histamine plays a crucial role in the brain, largely controlling a number of cognitive functions. It helps us to keep alert, to maintain concentration, and to stay awake. If histamine were prevented from working in the body, not only would our allergies dis­appear, but we would also find it difficult to be attentive, we might fall asleep or generally be more careless and lax. Children and students would find it particularly difficult to keep up in class and be affected especially around exam time. They might end up falling so far behind that they would eventually give up. Adults might experience danger­ous repercussions, such as falling asleep at the wheel of the car, failing to operate machinery safely, or making bad decisions that could affect both themselves and others. It is not feasible, therefore, to stop the body’s natural production of histamine.

Older versus newer antihistamines

There is plenty of evidence that the older antihistamines are accom­panied by some of the above-mentioned effects. For instance, they have been seen to contribute to poor learning in schools, and to road accidents, as they affect the brain in a similar way to alcohol. In a small number of people, they have been known to cause difficulty in urinating, increased pressure in the eyes (glaucoma), cloudiness of the eye lens (cataract), or damage to the cornea, the transparent layer that forms the front of the eye. These eye conditions can all lead to gradual loss of sight. Other possible side effects of these antihistamines include headaches, dry mouth and throat, nausea and digestive problems.

It’s fortunate that the newer antihistamines are vastly improved and have been prepared in such a way that they are prevented from reach­ing the brain from the bloodstream. They are just as efficient in treat­ing hay fever symptoms but have minimal adverse effect on cognitive function.

In general, the older antihistamines such as chlorpheniramine (brand name Piriton) are now only prescribed by doctors in special circum­stances. Even very young children, between ages two and five, should not be given the older ones, unless prescribed to induce sleepiness for some reason. One possible reason for inducing sleepiness in a child may be to minimize itching in severe eczema.

If you have been taking one of the older antihistamines for several years, you would be well advised to ask your doctor for one of the newer variety. Unfortunately, the older antihistamines are still on sale over the counter and, due to their lower cost, may appear more attrac­tive. Expert medical opinion would state, however, that drowsiness is an unacceptable side effect and these older drugs should not be used. It is hoped that they are withdrawn from over-the-counter purchase in the near future.

The new antihistamines are considered very safe. Potentially, they can cause the same side effects as the older antihistamines, but they are far less likely to do so. However, when taken in tablet form they can in­teract with other medications you may be taking, so it is important to mention these when seeing your doctor. Antihistamines also have the potential to interact with alcohol, so it is best to ensure that you drink nothing or very little while taking them. Read the instruction leaflet very carefully.

Usage of antihistamines

Antihistamines are the mainstay of hay fever treatment and certain other allergies. They generally come in tablet form or as a nasal spray and effectively ease symptoms related to the nose and eyes. They can also stop the terrible itching sensations in the throat, soft palate and ears.

However, they are not so useful at relieving nasal blockage, and other medications may have to be used in conjunction with antihistamines.

All in all, the only other hay fever medications that are equally ef­fective are steroid based – in the form of tablet or injection – and im­munotherapy. Steroidal medications and immunotherapy treatment both carry side effects not shared by antihistamines.

Availability of the newer antihistamines

Antihistamines currently available over the counter in the UK include the following:

• loratadine (brand names Clarityn, Clarityne and Claritin)

• acrivastine (brand names Benadryl, Semprex and Allergy Relief Capsules)

• cetirizine (brand names Zyrtec and Zirtec).

Antihistamines currently available on prescription in the UK include the following:

• fexofenadine (brand names Telfast 120, or Allegra in the USA)

• desloratadine (brand name Neoclarityn)

• mizolastine (brand name Mizollen).

Due to their adverse side effects, two antihistamines, astemizole and ter-fenadine, have been withdrawn from use in recent years – death from an irregular heartbeat was even a risk. If you still have old supplies in your medicine cabinet, ask your doctor whether it is safe for you to use them. You are likely to be offered a prescription for a newer antihistamine.

Effectiveness and speed of action

As with all medications, the effectiveness of different antihistamines varies, as does the length of time for which it provides relief and the degree of sleepiness it causes, if any. For instance, acrivastine is reported to take effect more rapidly than other antihistamines. Generally, how­ever, the newer antihistamines start working in less than an hour. Acrivastine is different from the rest of its family of medications too in that it is taken three times a day – the others are taken only once a day.

Pregnancy and breastfeeding

Not all of the newer antihistamines have been around for long enough for their effect on unborn babies and breastfeeding babies to be system­atically calculated. However, women who have not realized they were pregnant for several months have taken the new antihistamines with no adverse effect to the child. It can be said, therefore, that they have already been safely used by many thousands of pregnant women.

Of course, a small percentage of women will always give birth to babies with a mental or physical disability, and any medications taken during the early stages of pregnancy will always be queried by doctors and parents alike. The fact that there have been no reports of harm to the newborn for the mother taking the new antihistamines has, then, to be a mark of their safety.

It should also be said that the older antihistamines were subjected to rigorous research and there was no evidence of their being a risk to an unborn child – and the newer drugs are all based on their older forebears. For instance, fexofenadine is classed as fairly new, but its commonly used predecessor, terfenadine, is actually converted into fexofenadine in the body. In similar fashion, loratadine, which has been used for a number of years, produces desloratadine in the body, which strongly suggests that the new antihistamine desloratadine will also be safe. If you are pregnant, it is still well worth discussing with your doctor the possible benefits and risks of taking an antihistamine. Great caution in taking any medication will always be advocated, but your doctor is unlikely to want you to put up with difficult symptoms when there is a good available treatment – even though it has a pos­sible tiny (and as yet unrecognized) risk.

As there have been no reports of side effects in a nursing infant, an­tihistamine medications are also believed to be safe for a breastfeeding mother to take.

Antihistamine nasal sprays

As explained earlier, an excessive amount of histamine and other inflam­matory chemicals that occur naturally in the human body are produced from the mast cells when they come into contact with an allergen. The histamine sets up an inflammatory action to rid the body of the allergen, giving rise to the symptoms of hay fever in the process. Antihistamines work by very cleverly rushing to the areas where histamine becomes more active and effectively blocking the inflammatory action.

When antihistamines are delivered by nasal spray, there is usually good symptom relief and many people find that they don’t need to take tablets, which get into the whole body. Currently, the only anti­histamine available in a nasal spray is azelastin hydrochloride (brand name Astelin), which is obtainable on prescription. Its possible side effects include a bitter taste, headache, nose bleeds, nasal burning, dry mouth, fatigue, dizziness and nausea. As the spray usually takes seven to ten days to reach its maximum effectiveness, it is best to start using it prior to the start of the hay fever season.

As with the antihistamines taken in tablet form, the antihistamine nasal spray is considered safe during pregnancy and breastfeeding.