Allergic rhinitis

Article Abstract:

The most common form of atopy or allergy is allergic rhinitis, sometimes colloquially referred to as ''hay fever''. An in-depth review of the causes and treatments for allergic rhinitis is provided. Allergic rhinitis begins with the sensitization of an individual to specific substances, called antigens, by virtue of their ability to stimulate an antibody response. These antigens may be from pollen, dog and cat dander, or the tiny mites that live on house dust. In contrast to many immune responses, however, the response of some people to these antigens results in the production of antibodies of the IgE class. When the sensitized individual is again confronted with the specific antigens to which he has been sensitized, the antigen molecules are bound by the IgE antibodies. The complex of antigens and antibodies then binds to specific IgE receptors on mast cells. These mast cells then cough up large amounts of different substances, resulting in the familiar symptoms of allergy: sneezing, congestion, and runny nose. Of the many substances released by the mast cells, histamine is one of the most potent, and by itself can produce most allergy symptoms. It is not surprising, therefore, that many allergy remedies are of the class called ''antihistamines''. There are three types of histamine receptors in the body, however. The H1 receptors play a large role in the symptoms of allergy, while the H2 receptors are more involved in regulating the secretion of stomach acid. H3 receptors exist in the brain. The earliest antihistamines blocked the action of the H1 receptor, but also got into the brain and blocked the H3 receptor as well. This is why some antihistamines cause drowsiness. Newer antihistamines are designed to have a more difficult time entering the brain and therefore cause less drowsiness. In addition to the various drugs used to treat allergy symptoms, immunotherapy is also discussed. Immunotherapy is the controlled injection of the very antigen to which the patient is allergic. It is possible to desensitize the patient in this way, although many injections are needed and the desensitization is not permanent. This treatment should be reserved for the most allergic individuals, and those who do not benefit from drug therapy. Though the chances are small in the hands of a careful allergist, immunotherapy always involves the risk of fatal anaphylactic shock. (Consumer Summary produced by Reliance Medical Information, Inc.)

Symptomatology, Signs and symptoms

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Reduced allergen-induced nasal congestion and leukotriene synthesis with an orally active 5-lipoxygenase inhibitor

Article Abstract:

Leukotrienes are a class of compounds which play an important role in many forms of inflammation. Leukotriene B4 and the sulfidopeptide leukotrienes, along with some related compounds, are thought to contribute to the allergic response, including allergen-induced nasal congestion. These compounds clearly result in allergy-like reactions when injected, and these same compounds may be found in nasal fluid after challenge with allergen. However, further investigation of the role of these compounds in allergic reactions has been hampered by the lack of a suitable inhibitor of the enzyme 5-lipoxygenase. The sulfidopeptide leukotrienes, leukotriene B4, and compounds such as 5-hydroxyeicosatetraenoic acid all result from the metabolism of arachidonic acid through a metabolic pathway requiring 5-lipoxygenase. The principle is simple: inhibit 5-lipoxygenase and reduce the synthesis of the leukotrienes. Only recently, however, has pharmaceutical research produced a drug which has the required properties. This experimental compound, called A-64077, has been shown to effectively reduce the activity of 5-lipoxygenase when taken orally. The role of leukotrienes in allergy was investigated by giving this enzyme inhibitor to eight volunteers with allergic rhinitis (nasal inflammation). When given an oral dose of A-64077 prior to nasal challenge with allergens, the subjects experienced significantly less nasal congestion. Reduced amounts of leukotriene B4 and 5-hydroxyeicosatetraenoic acid were found in the nasal fluid. Histamine release was not affected. The inhibition of 5-lipoxygenase was experimentally verified by showing that the synthesis of leukotriene in whole blood was inhibited. The results show that leukotrienes play an important role in the development of the allergic response, and that further research into the enzyme 5-lipoxygenase may provide new therapeutic approaches. (Consumer Summary produced by Reliance Medical Information, Inc.)

Arachidonic acid, Inflammation, Inflammation mediators, Leukotrienes, Respiratory allergy, Respiratory hypersensitivity

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