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When your immune system panics.

WHEN YOUR IMMUNE SYSTEM PANICS

An unexpected overreaction to drugs, foods, or insect venom can hurl an otherwise healthy person into shock.

It seems to erupt from nowhere: a young man, finishing his shift as a taxi driver, sits down to have a snack. Within seconds, he complains that he has a lump in his throat. Moments later he is gasping for air, and as the ambulance arrives, he loses consciousness. On arrival in the emergency room, the man suffers a respiratory arrest, and his heart stops briefly. As physicians treat him they wonder what evil can strike such a powerful blow: Drugs? Asthma? Clots in the lungs? Several hours later, in an intensive-care unit, he wakes up on a ventilator and gives us an answer: cashews.

He has mild allergies to many foods, he reveals, and just before falling ill he had eaten two nuts, precipitating the kingpin of allergic reactions--anaphylaxis, a violent systemic response to something (usually) eaten or injected. Although relatively rare, it is common enough that two new cases of anaphylaxis a week are referred to Dr. Gillian Shepherd, an allergy specialist at New York Hospital. Large skin-test studies with insect venom suggest that 15 percent of the population may be predisposed.

Antibiotics, nuts, seafood, and insect stings are the most common culprits, but even substances as seemingly innocuous as celery are implicated. Against the backdrop of the usual hospital disasters, full-blown anaphylaxis is an incomparable cataclysm, a Krakatoa boxed inside a body.

Timely treatment works. But it must be administered soon, sometimes within minutes, to be effective. Several hundred otherwise healthy people in the United States die each year after reactions to penicillin alone. Interest in how to prevent and treat attacks has recently been intensified in the South by the march of the imported fire ant; up to 2 percent of fire-ant bites may bring on anaphylaxis.

In every case of anaphylaxis, the patient has encountered the offending substance, sometimes harmlessly, in the past, though perhaps without being aware of it. People, for example, may be exposed to penicillin in trace amounts as a contaminant in milk.

At the time of first contact, the immune system manufactures specific molecules designed to protect the body, anti-bodies of a type called IgE. The antibodies, in effect, take a biochemical "mug shot" of the invader and remember it indefinitely. At the time of next exposure, the foreign invader, or allergen, is "caught" by this vigilant immunologic patrol squad. Then, for reasons not fully understood, the patrol squad gets mightily carried away, setting into motion the release of chemical weapons--notably histamine and leukotrienes--that attack the lungs, blood vessels, intestine, and skin. Anaphylaxis in Greek translates as "backward protection." Indeed, in anaphylaxis, the misguided immune system attempts to keep out a foreigner by burning down the house.

The first manifestations of anaphylaxis begin seconds to two hours after exposure to the allergen. The reaction commonly starts with itching and flushing, hives, or a lump in the throat. Oddly, even in these early stages, victims may sense that something terrible is afoot, their fear wildly out of proportion to their symptoms. Heart-attack victims may also experience such premonitions.

The reaction bursts forth in one of several directions. Most patients will develop swelling of the airways, leading to audible wheezing and, in severe cases, respiratory obstruction. In others, the molecules attack primarily the walls of the blood vessels, leading to profound drops in blood pressure --and unconsciousness. Patients with food allergies are particularly prone to intestinal anaphylaxis--nausea, vomiting, diarrhea. Serious anaphylaxis often combines several of these ingredients.

It is virtually impossible to predict a first attack. One would expect people who suffer from lesser allergies, such as hay fever, to be predisposed. But studies of patients who have anaphylaxed to penicillin and wasp stings show no greater incidence of allergy than in the general population. Patients are more likely to react to substances injected into the blood --intravenous antibiotics or stings--than to swallowed allergens. But even oral antibiotics should never be taken lightly. Several years ago, a colleague took Bactrim, which she had taken before, for a minor infection. Fifteen minutes later, she developed a diffuse rash and collapsed from anaphylaxis.

Serious allergic reactions to foods often occur after consuming foods that people eat most often, because each repeat exposure further sensitizes, or agitates, the immune system. In Asia, rice is a major cause of allergic reaction.

Two factors--alcohol and exercise --seem to enhance otherwise mild or silent allergies, perhaps by increasing uptake from the stomach. I recall one young man with no history of anaphylaxis. He arrived in the emergency room itching and wheezing on the evening of his bachelor party. He had eaten a big lobster dinner, imbided a fifth of scotch, and run some drunken sprints--which in combination apparently precipitated a reaction. The dose of the allergen is also important. "The best time for an anaphylactic reaction," Dr. Shepherd says, "is at the end of a wedding. People drink too much. They dance. And they are exposed to all sorts of foods that they usually eat in small quantities."

Any allergic reaction that begins within minutes of eating food, receiving a sting, or taking a drug is cause for concern. Stories abound of patients who ignore hives or pop anti-histamines (which cannot reverse a serious reaction) and end up two hours later in shock. One woman ignored hives after a jellyfish sting and passed out at sea.

The mainstay of therapy for anaphylaxis is repeated injections of epinephrine, or Adrenalin. The drug works within seconds, but it is short-lived, and symptoms often recur with their own savage rhythm until the allergen is sufficiently dispersed in the body or is removed. In the case of food allergies, patients may be given noxious syrup to induce vomiting, and medicine to stimulate diarrhea. If the reaction subsides readily--many clear with one shot--the patient is discharged after several hours. But severe anaphylaxis may necessitate cardiopulmonary resuscitation and intensive care.

The allergist's first challenge after anaphylaxis is to identify the offending substance. The patient's history often isolates a suspect. The allergist may analyze the patient's blood for the offending IgE antibody or conduct skin tests with tiny amounts of allergen to measure the reaction. But anaphylactic reactions, a complex interplay between patient and environment, sometimes demand clever detective work. Certain patients, for example, suffer anaphylaxis only when they eat celery and exercise; either stimulus alone does nothing. One patient has anaphylactic reactions to shrimp only during the week before her menses. Another reacts for unclear reasons to canned ham eaten in New Jersey, but not to the same brand consumed in Florida.

Each anaphylactic episode may be more serious than the last, so prevention is crucial. Patients with allergies to insect stings are now being "desensitized" with progressively concentrated solutions of venom; these injections are designed to cause the body to manufacture a "protective" antibody of the IgG class, which snags insect venom before it is seen by the hysterical IgE patrol squad.

The best protection against drug-and food-induced anaphylaxis is avoidance. Whenever you are about to receive a new drug, remind your physician about allergies, even minor reactions. Physicians forget. Labels frequently carry brand names you might not recognize--Dynapen, Wymox, and Augmentin, to name a few, are all penicillin derivatives. Last February the Annals of Allergy printed three tragic accounts of individuals who had known antibiotic allergies. They died after receiving medications from physicians. One was wearing a Medic Alert bracelet at the time of her death.

Avoidance is more difficult for people with serious food allergies. They may be sensitive to even microgram quantities of antigen, and for them dining out is like traversing a minefield. One man with a seafood allergy anaphylaxed after eating French fries that may have been cooked in oil used to fry fish. In a much-publicized case several years ago, a Brown University student with a nut allergy died after eating chili thickened with peanut butter.

One lifesaving innovation for such individuals is the EpiPen, a device available by prescription for about $25. Resembling a retractable ball-point, it automatically injects a dose of epinephrine. Dr. John Yunginger, a professor of pediatrics at the Mayo Medical School, advises all his patients who have had systemic allergic reactions to carry one. The EpiPen may calm symptoms en route to the emergency room, and "it dramatically reduces mental wear and tear," Dr. Yunginger says. "Anyone who's had an anaphylactic reaction lives with fear. They hear a buzzing in the kitchen and it's probably a fly. But, my god, what if it's a bee or wasp?"

Although I have no allergies, I usually bring along an EpiPen when I travel to the countryside, a practice I formerly always attributed to paranoia. I have since discovered that many colleagues do the same. One keeps one in his pocket at all times, "just in case." I suppose we all have dreams and nightmares about that potential moment when one injection, at a cost of a few dollars, could make the difference between life and death.
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Title Annotation:anaphylaxis, severe allergic reaction
Author:Rosenthal, Elisabeth
Publication:Saturday Evening Post
Date:Oct 1, 1989
Words:1513
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