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An allergy is a disorder of the immune system in which an exaggerated response occurs when a person is exposed to normally harmless environmental substances known as allergens.
An allergic person produces a specific type of antibody called immunoglobulin E, or IgE, in response to normally harmless substances such as certain foods or medicines, pollen, animal dander and mold. These IgE antibodies cause allergic reactions. If a person is exposed again to the allergen, the IgE antibodies stimulate cells called mast cells to release chemicals including histamine to destroy the “foreign” substance.
The release of histamine causes typical allergy symptoms such as runny nose; itchy, watery eyes; sneezing; asthma symptoms; hives; and, in severe cases, a drop in blood pressure. This is why antihistamines are the mainstay of treatment for allergies.
About 50 million Americans, or 1 in 6 people, have environmental allergies, or allergic rhinitis. Allergic disorders are the sixth leading cause of chronic illness in the United States, according to the Allergy Report from the American Academy of Allergy, Asthma and Immunology.
People with seasonal allergic rhinitis (hay fever) experience symptoms during the time of year when certain allergens are in the air outdoors. There are several allergy seasons: springtime, when plants bloom and tree pollen counts soar; summer, the season for grass and weed pollen allergies; and autumn, the time for ragweed and mold allergies. Perennial allergies, or year-round allergies, are typically caused by indoor allergies to dust mites, mold, cockroaches and pet dander.
A specific allergy is not usually inherited, but your tendency to develop allergies is often passed down through families. If both parents have allergies, their child is likely to have allergies. However, your chance of developing allergies seems to be greater if your mother has allergies.
There are two main theories. One blames our increasing immune system sensitivity to the many synthetic chemicals in today’s society. Another theory, known as the “hygiene hypothesis,” states that the human immune system is becoming more reactive to allergens because of modern hygiene and health care. Our immune system is designed to fight off viruses, bacteria, parasites and other microbes. However, with modern hygiene, sanitation, vaccines, antibiotics and health care, our immune system does not have many invaders to fight off, and so its attention and energy are re-directed to normally harmless foreign substances.
It normally works the other way around – people can grow into allergies. There are cases in which one allergy replaces another, such as with childhood food allergies. Children normally suffer from food allergies more than adults. Once they grow up, they may get rid of food allergies but then be affected by seasonal or environmental allergies. About 85% of children outgrow food allergies to milk, soy, egg and wheat, but only 20% outgrow a peanut allergy. Up to half of young children outgrow their asthma, but many find that their symptoms return later in life. For most children, eczema improves during childhood.
Allergic reactions can develop at any age, no matter how old you are. Since repeated exposure to certain allergens can cause an allergic reaction, it makes sense to develop allergies when you’re older, as you’ve had more time to be in contact with dust, dander, mold and pollen.
In some cases, yes. Severe and untreated hay fever may lead to asthma, sinusitis and other serious conditions. Atopic dermatitis or eczema can spread to secondary skin infections if they are not treated properly, and untreated asthma can lead to chronic symptoms. Early detection and treatment of all allergic diseases is important.
Allergies cannot be cured, but symptoms can be controlled using a combination of avoidance measures and medications, and allergen immunotherapy (allergy shots) when necessary.
An allergist/immunologist is a pediatrician or internist who has undergone two to three years of special training in the diagnosis and treatment of allergic and immunologic diseases. To understand what you are allergic to, an allergist will:
- Take a personalized patient history, including a thorough record of the illness, a family history, and information on home and work/school environments
- Perform allergy testing
- Possibly perform other laboratory tests
An allergist can create a management plan with you for better control of your environment and your symptoms. Your plan may also include proper medication and, if necessary, allergen immunotherapy (allergy shots).
Avoidance is the best treatment for any allergic disease. If you avoid the allergen, you'll avoid the allergic reaction. Diagnosis and education are crucial steps in allergen avoidance. Educated allergy and asthma sufferers fare much better than those who do not understand their condition.
