Allergies affect as many as 50 million Americans, with more than half of the population testing positive for at least one allergy, reports the American Academy of Allergy, Asthma and Immunology, or AAAAI. Allergies are an overreaction of the immune system to a normally innocent substance, such as peanuts or pollen. The body of an allergic person produces an oversupply of chemicals and proteins to get rid of the offending substance, called an allergen. These chemicals produce the symptoms related to allergic diseases, such as hay fever, eczema, asthma and dermatitis.
Food
Food causes allergic reactions in around 3 to 4 percent of adults and 6 percent of children in the U.S. In "Food Allergy: Practice Parameter," the AAAAI notes that the most common causes of allergies in children are cows' milk, hens' eggs, peanuts, nuts, soybeans and wheat. The most common causes of food allergies in adults are peanuts, tree nuts, fish, shellfish, fruits and vegetables. People with food allergies may have reactions upon touching or eating food with an allergenic ingredient, or by inhaling fumes from cooking or manufacturing the food. For instance, a person with milk allergy may react simply by touching or smelling cake made with milk, or breathing in fumes of food cooked in butter. Food allergies are difficult to diagnose because many prepared foods contain hidden ingredients that may cause an allergic reaction. Also, most persons allergic to one kind of food will react to other kinds. For example, a person with shrimp allergy will most likely react to crab or lobster.
Airborne Allergens
Airborne allergens cause more than 35 million Americans to suffer from allergic reactions or asthma, according to the National Institutes of Health. As the name implies, airborne allergens are tiny particles light enough to be carried by air. Examples of airborne allergens are pollen, house dust mites, molds, pet dander and chemicals from paints, cigarette smoke, carpeting or perfumes. Pollen is the most common cause of airborne allergies, because it is not easily avoidable or controlled. Pollen from trees, grasses and weeds may trigger allergic reactions from one season to the next. Mold and dust mites are other important causes of yearlong allergies, especially in inner-city homes where ventilation is a problem. Molds grow in warm, damp places both indoors and outdoors. Dust mites live in the dust found in all homes and offices, and they are difficult to eradicate. The waste products and dead body parts of the mites provoke the allergic reactions.
Latex
Latex is made from the milky substance of a Brazilian rubber tree, and it is used in many consumer and medical products such as gloves, balloons, toys, bottle nipples, surgical masks and tubings. The Asthma and Allergy Foundation of America points out that latex allergies are rare among the general U.S. population, but it has become a major occupational health problem in high-risk groups. The group with the highest risk for latex allergy is children with a genetic spinal condition called spina bifida. Children who undergo frequent, repeated or lengthy surgeries are also at high risk for developing latex allergies. Latex also causes allergies in among 5 to 15 percent of health care workers.
Insect Sting
For most people, an insect sting will cause a mild itchy rash or swelling, but the skin usually returns to normal in a few hours. However, about 3 percent of adults and 0.8 percent of children will experience life-threatening allergic reactions to insect stings. This reaction, called anaphylaxis, develops within minutes and affects the entire body, causing symptoms such as difficulty breathing; nausea; fainting; itchiness; swelling of the throat, lips or tongue; blocked airways; rapid pulse; and shock. The AAAAI lists insects that may cause anaphylactic shock include yellow jackets, honeybees, paper wasps, hornets and fire ants.
