HAYFEVER

Hayfever is inflammation of the nasal lining due to an allergy to pollen. Hay fever is also known as seasonal allergic rhinitis.

Causes

Allergies are caused by an oversensitive immune system, leading to a misdirected immune response. The immune system normally protects the body against harmful substances such as bacteria and viruses. Allergy occurs when the immune system reacts to substances (allergens) that are generally harmless and in most people do not cause an immune response.

As noted above, hay fever involves an allergic reaction to pollen. A virtually identical reaction occurs with allergy to mold, animal dander, dust, and similar inhaled allergens. Particulate matter in polluted air and chemicals such as chlorine and detergents, which can normally be tolerated, can greatly aggravate the condition.

The pollens that cause hay fever vary from person to person and from region to region; generally speaking, the tiny, hardly visible pollens of wind-pollinated plants are the predominant culprits. Pollens of insect-pollinated plants are too large to remain airborne and pose no risk. Examples of plants commonly responsible for hay fever include:

* Trees: such as birch (Betula), alder (Alnus), hazel (Corylus), hornbeam (Carpinus), horse chestnut (Aesculus), willow (Salix), poplar (Populus), plane (Platanus), linden/lime (Tilia) and olive (Olea). In northern latitudes birch is considered to be the most important allergenic tree pollen, with an estimated 15-20% of hay fever sufferers sensitive to birch pollen grains. Olive pollen is most predominant in Mediterranean regions.
* Grasses (Family Poaceae): especially rye (Lolium sp.) and timothy (Phleum pratense). An estimated 90% of hay fever sufferers are allergic to grass pollen.
* Weeds:ragweed (Ambrosia), plantain (Plantago), nettle/parietaria (Urticaceae), mugwort (Artemisia), Fat hen (Chenopodium) and sorrel/dock (Rumex)

In addition to individual sensitivity and geographic differences in local plant populations, the amount of pollen in the air can be a factor in whether hay fever symptoms develop. Hot, dry, windy days are more likely to have increased amounts of pollen in the air than cool, damp, rainy days when most pollen is washed to the ground. Interestingly however, many sufferers will experience the worst symptoms during rainy days.

The time of year at which hay fever symptoms manifest themselves varies greatly depending on the types of pollen to which an allergic reaction is produced. As most pollens are produced at fixed periods in the year, a long-term hay fever sufferer may also be able to anticipate when the symptoms are most likely to begin and end, although this may be complicated by an allergy to dust particles.

When an allergen such as pollen or dust is inhaled by a person with a sensitized immune system, it triggers antibody production. These antibodies mostly bind to mast cells, which contain histamine. When the antibodies are stimulated by pollen and dust, histamine (and other chemicals) are released. This causes itching, swelling, and mucus production. Symptoms vary in severity from person to person. Very sensitive individuals can experience hives or other rashes.

Some disorders may be associated with allergies. These include eczema and asthma, among others.

Allergies are common. Heredity and environmental exposures may contribute to a predisposition to allergies.

Symptoms

The effect of hayfever can vary greatly: some people may only be mildly afflicted, whereas others may suffer greatly. Common symptoms include:

* coughing
* headache
* itching nose, mouth, eyes, throat, skin, or any area exposed to the allergen.
* runny nose (and occasionally nosebleeds)
* impaired smell (and thus sensitivity to flavours)
* sneezing
* stuffy nose (nasal congestion)
* watering eyes
* sore throat
* wheezing
* fever
* cross-reactivity allergy to some fruits
* conjunctivitis

Signs and tests

The history of the person's symptoms is important in diagnosing allergic rhinitis, including whether the symptoms vary according to time of day or the season; exposure to pets or other allergens; and diet changes.

Allergy testing may reveal the specific allergens the person is reacting to. Skin testing is the most common method of allergy testing. This may include intradermal, scratch, patch, or other tests. Less commonly, the suspected allergen is dissolved and dropped onto the lower eyelid as a means of testing for allergies. (This test should only be done by a physician, never the patient, since it can be harmful if done improperly.)

In some individuals who cannot undergo skin testing (as determined by the doctor), the RAST blood test may be helpful in determining specific allergen sensitivity.

Sufferers might also find that cross-reactivity occurs. For example, someone allergic to birch pollen may also find that they have an allergic reaction to the skin of apples or potatoes. A clear sign of this is the occurrence of an itchy throat after eating an apple or sneezing when peeling potatoes. This occurs because of similarities in the proteins of the pollen and the food. There are many cross-reacting substances.

Prevention

Avoiding exposure to pollen is the best way to decrease allergic symptoms.

* Remain indoors in the morning and evening when outdoor pollen levels are highest.
* Wear face masks designed to filter out pollen if you must be outdoors.
* Keep windows closed and use the air conditioner if possible in the house and car.
* Do not dry clothes outdoors.
* Avoid unnecessary exposure to other environmental irritants such as insect sprays, tobacco smoke, air pollution, and fresh tar or paint.
* Avoid mowing the grass or doing other yard work, if possible.
* Regular hand- and face-washing removes pollen from areas where it is likely to enter the nose.
* A small amount of vaseline around the eyes and nostrils will stop some pollen from entering the areas that cause a reaction
* It may be helpful to humidify the room you are in to help clean the allergens out of the air, perhaps by using a humidifier, leaving a bowl of water around or leaving a wet towel in the room.
* You may find it useful to breathe through a wet towel or tissue when you feel the symptoms are acute, if you don't have access to a face mask.

Treatment

The goal of treatment is to reduce allergy symptoms caused by the inflammation of affected tissues. The best "treatment" is to avoid what causes your allergic symptoms in the first place.

Medication

The most appropriate medication depends on the type and severity of symptoms. Specific illnesses that are caused by allergies (such as asthma and eczema) may require other treatments.

Options include the following:

* Fast-acting strong antihistamines such as drugs including chlorphenamine which relieve the symptoms after a hayfever "attack".
* Short-acting antihistamines, which are generally over-the-counter (non-prescription), often relieve mild to moderate symptoms, but can cause drowsiness. A pediatrician should be consulted before using these medicines in children, as they may affect learning. One formerly prescription medication, loratadine (Claritin®), is now available over the counter in many countries. It does not tend to cause drowsiness or affect learning in children. Azelastine (Astelin®) is the only antihistamine available as a nasal spray.
* Longer-acting antihistamines cause less drowsiness, can be equally effective, and usually do not interfere with learning. These medications include fexofenadine (Allegra), and cetirizine (Zyrtec).
* New leukotriene receptor antagonists, such as montelukast (Singulair) and zafirlukast (Accolate) have proven very effective in dealing with allergic rhinitis, without the common side-effects of the first-generation antihistimines, such as drowsiness. These medicines are also long-acting, and are recommended to be taken once-daily.
* Corticosteroid nasal sprays are effective and somewhat safe, and may be effective without oral antihistamines. These medications include fluticasone (Flonase/Flixonase), budesonide (Rhinocort), mometasone (Nasonex), triamcinolone (Nasacort) and beclomethasone (Beconase®).
* Topical decongestants may also be helpful in reducing symptoms such as nasal congestion, but should not be used for long periods as stopping them after protracted use can lead to a rebound nasal congestion (Rhinitis medicamentosa).
* Cromolyn sodium (or cromoglycate) is a drug that stabilizes mast cells and prevent their degranulation and subsequent release of histamine. It is available as a nasal spray (Nasalcrom) for treating hay fever. Eye drop versions of cromolyn sodium (Crolom) are available for allergic conjunctivitis.
* "Allergy shots" (Hyposensibilization, immunotherapy) are occasionally recommended if the allergen cannot be avoided and if symptoms are hard to control. This includes regular injections of the allergen, given in increasing doses (each dose is slightly larger than the previous dose) that may help the body adjust to the antigen. These tend to be offered as a last resort as the therapy is more expensive and can increase the risk of triggering a secondary allergic reaction such as an asthma attack.

Source: wikipedia GFDL