The occasional skin reaction to a drug or plant, the last in this group of allergy emergencies, can become so extensive that it poses a real danger. Poison ivy or oak may produce such a skin reaction. The skin may blister. Intact skin protects against bacteria and allows the exchange of salts and water needed to prevent the body from overheating. If enough skin is involved, the victim risks complications from the partial loss of skin. If damage to the skin is extensive enough, fever, chills, skin abscesses, and blood-borne infections may occur. The skin inflammation (dermatitis) that results from contact with poison ivy, cosmetics, metals, or chemicals is called, appropriately, contact dermatitis; antibodies are not involved. Cells called lympho­cytes become sensitized to the chemicals and, upon reexposure to the chemicals, enter the skin in an effort to remove the invading material. In the ensuing effort, the lymphocytes call in helper cells —macro­phages. Macrophages, literally "big eaters," may damage normal tissue in the process of clearing up the invaders. It generally takes about forty-eight hours after the chemical enters and the cells re­spond for skin damage to be visible. An even more severe dermatitis may result —not from external contact this time, but from drugs taken internally. Some of the earlier, long-acting sulfa preparations were responsible for such severe blistering that large areas of the skin were shed, a condition physicians call exfoliative dermatitis. Today, few of the drugs com­monly used cause such reactions. It is always possible, however, that a new drug will be approved before an adverse reaction is discovered. Severe anaphylaxis, unremitting asthma, acute edema of the larynx, and extensive contact (or exfoliative) dermatitis must all be considered true emergencies. Emergencies, though, may also arise from the side effects of the drugs used to treat these and other allergic diseases. Serious side effects are usually due to a relative over­dose of a drug. The overdose may be caused not only by receiving or taking more than the usually prescribed amount but because of the body’s metabolism of the particular drug or because the excretion is slower than normal. The end result is an accumulation of high or toxic levels of the drug or drugs. Among antiallergy drugs, the bronchodilators used to treat asthma cause the bulk of serious side effects. (A list of undesirable reactions appears in Table 3.3.) Nonemergency Allergic Reactions The conditions described below are more annoying than danger­ous. Familiarity with their symptoms and causes should alleviate alarm and lead to proper treatment.

Atopic dermatitis is characterized by chronically itchy, superficially inflamed skin, often accompanied by allergic symp­toms such as hay fever and asthma. It also occurs in patients whose families have histories of allergies. The disease frequently occurs on the face and at or near the elbows and knees. Although atopic derma­titis is associated with allergies, the skin lesions do not have an allergic mechanism in most patients. Symptoms are commonly worse during the cold part of the year and are aggravated by contact irritants. In some people, skin symptoms appear to be aggravated in part by cer­tain foods or by exposure to inhaled allergens such as pollen.

Once one has been diagnosed as having a particular food allergy, life is not over. On the contrary, a new life can begin when one knows the foods that are safe to eat —and the ones that are not.

When the exact cause of the food allergy remains unknown after all diagnostic tests have been completed, your doctor may prescribe drugs to alleviate the symptoms. (Unfortunately, such drugs cannol cure the allergy itself.) Another approach is the rotary diet, in which no food is repeated within a five-day span, thus reducing symptoms.

Egg allergy is less common than milk allergy, but the allergic threshold is much lower. Sometimes, merely touching or smelling an egg can produce symptoms. This also happens when one is given vaccines for measles, mumps, rubella, and flu, all of which vaccines are made with eggs. Any egg, be it chicken, goose, duck, or turkey, can produce symptoms if you have an egg allergy. The avoidance list also includes eggs in any form, fresh, dried, or powdered, as well as yolk and albumin. Candy is often brushed with egg white for luster, and pies are, too, so that they bake to a golden brown. Coffee and homemade beer, as well as some soups, may be clarified with egg shells. Generally speaking, you should beware of such foods as waffles, cakes, pastries, ice cream, and sherbet (unless made from an egg-free powder), creamy salad dressings and mayonnaise, heavy sauces, bouillon and broths, root beer, Ovaltine and Ovomalt, meat loaf and sausages, noodles, and baking products. Egg-free meals can be prepared in a variety of ways. Ener-G-Foods’ Egg Replacer (formerly Jolly Joan) is one of the most readily available egg substitutes. You can also replace one egg by mixing 2 tablespoons of flour, V2 teaspoon of shortening, Vz teaspoon of baking powder, and 2 tablespoons of liquid. A package of Knox gelatin or a mashed banana can be used as a binder for each missing egg. Not all cake mixes absolutely require eggs. If you wish, you may write to the company making a particular recipe and ask for in­formation. Many so-called egg substitutes available today are not egg-free, as they contain egg whites, the major source of egg allergen for most people. Remember to eat plenty of meat, fish, poultry, liver, cheese, dried beans, or nuts to get the amount of protein and В vitamins usually derived from eggs.

В cells, or В lymphocytes, are lymphocytes derived from the bone marrow. They are involved in the production of antibodies.

Farmer’s lung is a form of allergic lung disorder caused by exposure to moldy hay. See also Hypersensitivity Pneu­monitis.

An allergy is an abnormal reaction to an ordinarily harmless sub­stance or substances. These substances, called allergens, may be in­haled, swallowed, injected, or contacted by the skin.

An allergy is a reaction, usually between antibodies, or specific proteins, manufactured by the body of an allergic person and foreign proteins inhaled or ingested by that person. The result is a release of allergic mediators, humoral substances produced by the body that are capable of causing such undesirable effects as itching, redness, runny nose, and wheezing. Sometimes, instead of causing the re­lease of chemical mediators, the foreign substances that are present produce a reaction of lymphocytes and macrophages —a cellular rather than a humoral response. Any attempt to understand allergic reactions raises numerous important questions. What makes someone "allergic," that is, capable of reacting to inhaled or ingested proteins, or both, in a potentially dangerous way, whereas someone else has no reaction at all? How is this allergic potential passed from generation to generation? How is a person’s ability to be allergic modulated? Can this potential be controlled? How does this allergic potential change as people change? Can they "grow into" or "out of" allergies, and can they influence whether they do this by what they eat and breathe? The answers to these questions have much to do with whether a person is allergic. But just as many questions remain about specific allergic conditions. For example, why do some people have rashes while others have hay fever, and still others, asthma? Why do young children often develop eczema first and then rhinitis, finally becom­ing asthmatic? Is medical science capable of halting the progression from one allergic problem to another? What is different about an allergic person who experiences only hay fever, and one who suffers from asthma? Why are an asthmatic’s lungs sensitive to environmental stimuli, while the sensitivity of the sufferer from hay fever is confined to the nose? What about the drugs that are now used for allergic disease? Do we know the optimal doses of drugs for skin rashes, rhinitis, and asthma? How do physicians go about weighing drug risks against benefits? What is the theoretical basis for the many pharmacologic agents used today?

Uses Adrenal corticosteroids are effective drugs in treating nearly all allergic disorders. When used over long periods, however, their poten­tial for causing serious side effects limits their usefulness in treating hay fever, eczema, or long-term hives. They are used to relieve acute, chronic asthma that cannot be controlled by other treatment and to treat allergic pneumonia and serum sickness (various combinations of arthritis, rashes, fever, and swollen lymph nodes, or "glands"). Corticosteroids are also used to treat asthma patients who have had to take steroids recently and who now must undergo surgery, or who are having other physical stress. Corticosteroids are sometimes used in cases of acute hives, acute reactions involving multiple organ sys­tems, or for reactions to drugs, serum, or transfusions. Representative Drugs Corticotropin (ACTH, Acthar, and H.P. Acthar Gel) is a hormone secreted by the pituitary that stimulates the release of cortisone by the adrenal glands. The results of treat­ment with this drug are unpredictable, though, and it has no advan­tages over therapy with adrenal corticosteroids or similar drugs. Cortisone (Cortone) and hydrocortisone (available under several trade names) are fast-acting steroids used briefly during treatment of life-threatening forms of asthma, for reactions involving more than one organ system, and for other acute conditions. Methylprednisolone (Medrol and Solu-Medrol), prednisolone (available under various trade names), and prednisone (also avail­able under various trade names) are fast-acting preparations that are active over brief periods. Useful in treating acute allergic conditions, they are also suitable for administration on alternate days in cases requiring prolonged therapy. Alternate-day administration has been shown to reduce many adverse effects of prolonged steroid therapy. Depo-Medrol, a long-acting, injectable form of methylprednisolone, is also available. Cloprednol, another corticosteroid, is active over a shorter period than either methylprednisolone, prednisolone, or prednisone. Yet it may offer the same advantages in alternate-day therapy as the other three. Cloprednol, however, is still experimental and is not licensed by the Food and Drug Administration. Some long-acting corticosteroid derivatives are betamethasone (Celestone), dexamethasone (available under various trade names), fluprednisolone (Alphadrol), paramethasone acetate (Haldrone), and triamcinolone (Aristocort and Kenacort). These compounds are not suitable for alternate-day therapy.