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Allergy: Overview, Facts and Types

Allergy is an abnormal reaction of the body’s immune system response to substances that are generally harmless for most people. These substances are known as allergens and are found in foods, pollen, dust mites, molds, pets, insects, and some medicines.

If you have an allergy, your immune system overreacts to an allergen by producing antibodies called Immunoglobulin E (IgE). These antibodies attach themselves to a type of immune cell called a mast cell.

When the allergen comes into contact with the antibodies, these mast cells respond by releasing certain chemicals into the bloodstream, one of which is called histamine. Histamine causes the tiny blood vessels in the tissues of your body to leak fluid, resulting in a number of different symptoms which are extremely irritating and uncomfortable.

Approximately 50 million Americans suffer from some type of allergies, according to the Asthma and Allergy Foundation of America (AAFA). They are most common in young children but can affect people of all ages.

Facts About Allergies

  • Allergies are the sixth leading cause of chronic illness in the United States and the third most common chronic disease among children under 18 years.
  • Allergic rhinitis (hay fever) affects between 10 and 30 percent of all adults and as many as 40 percent of children worldwide.
  • Allergies can be seasonal (occurring during certain times of the year, such as pollen allergy in the spring) or perennial (occurring year-round, such as dust mite or pet allergy).
  • Immunotherapy (allergy shots) helps reduce hay fever symptoms in about 85 percent of people with allergic rhinitis.

Types of Allergies

Food allergy

A food allergy occurs when the body’s immune system sees a certain food as harmful and reacts by causing allergic symptoms. Food allergy is more common in children, but they can appear at any age.

House dust mite allergy

House dust mite allergy occurs when a person has a hypersensitivity reaction to allergens from the house dust mite. House dust mite allergy is the most common cause of year-round allergy and asthma.

Pollen allergy

Pollen allergy is an allergic reaction to pollen from trees, weeds, and grasses. It is one of the most common triggers of seasonal allergies.

People can be allergic to different types of pollen. For instance, some people are allergic to pollen from beech trees; others are allergic to pollen from grasses.

Mold allergy

Mold allergy is an allergic reaction caused by exposure to mold spores in indoor or outdoor areas. You may be more likely to develop a mold allergy if your home or your workplace is high in humidity or moisture, or has poor ventilation.

Latex allergy

Latex allergy is an allergic reaction to certain proteins found in natural rubber latex, a product made primarily from the rubber tree. Latex allergy generally develops after repeated exposure to products containing natural rubber latex. Allergy to latex is an increasing health problem.

Latex allergy may cause allergic reactions ranging from skin irritation to anaphylaxis, a potentially life-threatening condition.

Pet allergy

Pet allergy is an allergic reaction to proteins found in an animal’s saliva, skin cells, or urine. Allergies to animals can take two years or more to develop and may not disappear until 6 months or more after ending contact with the animal.

Pet allergens can collect on furniture and other surfaces, and can remain in them for several months. In addition, these allergens can stay in household air for months after the animal has been removed. Allergies to pets, particularly to dogs and cats, are a common cause of allergic disease, including asthma and hay fever.

Insect sting allergy

Insect sting allergy is an allergic response to the bite or sting of an insect. Most people stung or bitten by insects suffer pain, redness, itching and minor swelling in the area around the bite or sting.

People can have a serious allergic reaction (anaphylaxis) to stinging or biting insects. Without immediate treatment, anaphylaxis may cause death. Symptoms usually involve more than one organ system, such as the skin, the lungs, the heart, and the gut.

Drug allergy

Drug allergy is an allergic reaction to certain medications either comes in pill, liquid, or injectable form. The most common cause of drug allergy is penicillin and the other drugs that can cause allergy reactions include sulfa drugs (such as Septra and Bactrim), aspirin, ibuprofen, and chemotherapy drugs.

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