Allergy Resources

Allergy Resources

What is allergy?
Medically speaking, an allergic response is an overreaction of the immune system. Although most people think allergic and asthmatic patients have deficient immune systems, the contrary is true. If you're allergic, it's because (lucky you) you've inherited certain genes that make your immune system hyper responsive.

Allergy occurs when this hyper alert immune system, poised to rout bacteria and viruses, goes overboard. Like a nervous policeman patrolling a dark alley, the oversensitive immune system reacts to every little thing. Even harmless substances such as cat dander or house dust are perceived as threatening invaders. These normally harmless substances are called allergens. The body then gears up for war, and produces protein molecules known as antibodies (a specific kind called immunoglobulin E, or IgE) to fight the allergens. The antibodies attach themselves to mast cells, tiny time bombs plentiful in the respiratory and gastrointestinal tracts. When the mast cells explode, they release a load of chemicals, including histamine, a powerful substance that causes symptoms.

Allergic rhinitis, or hay fever, the most common form of allergy, involves the respiratory system—nasal cavity, mouth, throat, bronchi, lungs, and diaphragm—and often brings on its own mini-version of Niagara Falls.

But there are other types of allergy that affect various parts of the body. The area where symptoms appear is called a shock organ or target organ and may differ in each individual. For instance, milk may cause a skin rash in one person, abdominal cramps in another, and asthma in a third.

The eyes, ears, and gastrointestinal tract are other common shock organs; less commonly, the heart, bladder, blood vessels, kidneys, muscles, joints, brain, and central nervous system are affected. A person's shock organs can change with age. A baby girl's eczema, for example, might develop into hay fever as she grows.

Why me?
Children often wonder why their friends can cuddle kittens without getting hives, or play in the grass without getting a runny nose, and they ask themselves: "Why me? Why am I different?"

The answer is a bit complicated. Many factors play a role in the development of allergy, but the strongest is heredity. When one parent is allergic, the child runs a 50 percent chance of inheriting the tendency. When both parents are allergic, the odds jump to 75 percent, although the child may not inherit the same symptoms or sensitivities to the same substances. Even if neither parent is allergic, anyone can become allergic at any time, if three conditions prevail.

1. The tendency to produce large quantities of immunoglobulin E, or IgE, a specific antibody present in allergic reactions.
2. Repeated exposure to the allergen, the substance that causes a reaction. Almost anything inhaled, eaten, touched, or injected into the body can become an allergen.
3. Sufficient potency and duration of exposure.

When all three factors are in play, the process is called sensitization. Say, for instance, that you're stung by a bee for the first time. You have no response, except maybe an "ouch!" But because you inherited the tendency to produce IgE, these antibodies form in your blood and circulate throughout your body. In other words, you've become sensitized.

Sometime later you get a second sting. Your immune system considers the bee venom a foreign invader and mobilizes the IgE antibodies to fight it, thus starting the chemical process that causes symptoms. Sensitization can happen after a single exposure or after many years of exposure, depending on how long a person's body takes to produce antibodies.

A few unfortunate souls acquire acute, potentially lethal sensitivity, especially to insect stings, certain foods such as peanuts and shellfish, sulfites and other additives, and drugs such as penicillin and aspirin.

For these people, the result of even a single bee sting or a peanut is anaphylaxis, a frightening condition that intensifies rapidly. It starts with breathing difficulty and a drop in blood pressure, and can proceed to unconsciousness, coma, and even death. Fortunately, anaphylaxis is rare and can be controlled and prevented. (See chapter 6.)

Over the threshold
In most cases, even after you become sensitized, not every encounter with an allergen will bring on a reaction. If you're allergic to strawberries, for instance, the question is: How many strawberries will trigger symptoms? One or two may not do it, but that third piece of fruit, because you've been "primed," will push you right over your allergy threshold. Doctors call this the priming effect.

Think of it as the proverbial straw that breaks the camel's back. You can endure a certain amount of exposure to pollen, molds, or other allergens without having symptoms. But once your system gets primed—that is, loaded to the point where you exceed your threshold—you begin to react.

Take a second example. You may be allergic to house dust but have no reaction when the concentration of dust in the air is low. Change the bedding, however, and you start to sniffle.

A combination of allergens can also shoot you over the threshold. Say you're watching television in a room with musty wallpaper. Mold spores are in the air but aren't bothering you. Suddenly, your cat comes in, jumps on your lap, and sets you off on a sneezing fit. Separately, the molds and cat dander might not affect you, but together—wham!

Another factor is air pollution. You may or may not be allergic to the chemicals themselves, but their effect is the same: to prime the body, that is, to make the mucous membranes more permeable and raise IgE levels. The result is that when even a small amount of allergen strikes, your immune system is so receptive that it bursts into action.

Particular pollutants to watch out for are natural gas (methane); PCBs (polychlorinated biphenyls), found in insulators, paints, and varnishes; smog (ozone); car exhaust (carbon monoxide); and tobacco smoke. A recent Swedish survey showed that mothers who smoked while pregnant quadrupled their chances of having an allergic baby.

Incidentally, there's some evidence that keeping a child solely on breast milk for six months may increase the child's resistance to food allergies later. Breast-feeding also protects the infant by delaying exposure to foods such as cow's milk, which often causes allergies.

A warning: The Reuters news service recently reported that goat's milk can trigger serious allergic reactions in infants already sensitive to cow's milk. This finding runs counter to the standard practice of substituting goat's milk for cow's milk in babies with this type of allergy.

Solid foods should be introduced gradually into the baby's diet so that any allergy will be easily found. The most common reactions are to cow's milk, wheat, eggs, chocolate, corn, and citrus fruits. Rice cereal is a safe introduction to solid foods.

Older children should be urged to eat a varied diet, as eating too much of the same foods can trigger sensitivities.

The first step
Before you rush off to an allergist, check with your primary-care doctor. Get a thorough physical exam, and remember that "allergy" can be a handy crutch for physicians who can't find anything wrong with you. Be sure to ask questions (see chapter 4) before accepting a diagnosis of allergy.

Technically, every human being has the potential to become allergic. People with no allergies have never exceeded their allergy thresholds. That's one reason why allergy shots usually work. They don't eliminate the allergy; rather, they raise your threshold so you can tolerate more of the substance before you get symptoms.

This threshold can vary during your lifetime. Emotional stress, a viral illness, fatigue, exposure to chemical irritants, overexertion, and severe weather conditions can lower your threshold and make you more reactive.

Eliminating tension, improving diet, and enjoying general good health can sometimes raise the threshold. Even age can help. One of the lesser-known advantages of the golden years is that because the immune system's efficiency begins to wane, IgE antibodies are less and less eager to challenge invading allergens. That's why older people have fewer allergic problems.

Nevertheless, even if you've passed the half-century mark, you may not be home free. New allergies can develop at any stage of life, particularly if you move to a location with different plant life, take up painting or other hobbies that use chemicals, or get a new puppy. Even allergies that have subsided can recur when allergen levels are high.

By now you've begun to realize that allergy is a complex subject that not everyone, including doctors, understands. Yet most will agree that allergy is an unwanted side effect of a civilization that brings us a constant influx of chemicals, products, and technologies. Those same technologies, however, enable doctors and scientists to explore new theories, conduct more effective studies, improve medication, and, in general, offer better treatment and broader horizons of hope to all who need it.