Issue link: https://wardsworld.wardsci.com/i/1464249
5 Allergy (continued) + ward ' s science 5100 West Henrietta Road • PO Box 92912 • Rochester, New York 14692-9012 • p: 800 962-2660 • wardsci.com This article was originally published by McGraw Hill's AccessScience. Click here to view and find more articles like this. and natural inhalation substances (for example, pollens) are the most frequently involved allergens. Anaphylaxis The most feared allergic reaction is an acute event known as anaphylactic shock. This is an IgE-mediated reaction with sudden onset, and symptoms develop within minutes after exposure to the triggering allergen. The victim may experience a feeling of great anxiety; symptoms include skin swelling, skin redness (often accompanied by hives), vomiting, abdominal cramps and diarrhea, life-threatening breathing difficulties (due to swelling of the throat), and severe bronchospasm. A drastic fall in blood pressure may cause fatal shock within a few minutes. Insect stings and drugs, including penicillins, are the most frequent causes of anaphylactic shock. Diagnosis The diagnosis of allergic diseases encompasses several facets. The large variety of clinical forms of allergic reactions and the multitude of concomitant allergens require prolonged observation and in-depth investigation of the individual's life habits. Because many clinical manifestations of allergy are mimicked by nonallergic mechanisms, it is usually necessary to use additional diagnostic procedures to ascertain whether the person has developed an immune response toward the incriminated allergen. Such procedures primarily consist of skin tests, in which a small amount of allergen is applied on the skin or injected into the skin. If the individual is sensitized, a local immediate reaction ensues, taking the form of a wheal (for IgE- mediated reactions), or swelling and redness occur after several hours (for delayed hypersensitivity reactions). The blood also may be analyzed for immunoglobulin antibodies by serological assays, and sensitized lymphocytes are investigated by cultur- ing them with the allergen. Overall, it is important to achieve as precise a diagnosis as possible because the discovery of the responsible allergen (or allergens) markedly influences therapy and facilitates prediction of the allergy's outcome. Therapy The most efficient treatment, following identification of the offending allergen, remains elimination of the allergen from the affected person's environment and avoidance of further exposure. This form of treatment is essential for allergies caused by most household and workplace allergens. Inflammatory reactions and corresponding symptoms caused by allergic mediators may be relieved by several drugs (for example, anti- histamines or steroids) that act as pharmacological antagonists to these mediators. Other drugs act at a more central level and influence the ease with which mast cells or basophils release their mediators. Because the state of hypersensitivity usually remains present over many years, especially when contact with the allergen is periodically renewed (as is the case with pollens), such an approach to allergy therapy may be only palliative. Attempts to influence the hypersensitive state itself in IgE- mediated allergy are more decisive. Repeated injections of increasing doses of allergen progressively diminish the degree of hypersensitivity. This procedure, which usually must be pur- sued over several years, is referred to as hyposensitization or immunotherapy.