An allergic reaction occurs when the body’s immune system reacts to a specific substance, known as an allergen. People are not born with allergies, but they develop over time as the immune system produces antibodies against the substance recognized as harmful. Subsequent exposure to the allergen triggers the immune system to release histamines resulting in the symptoms that may be mild, severe or even life-threatening. There are many different types of allergies classified by the type of allergen.
Seasonal
Seasonal allergies, also known as hay fever or allergic rhinitis, are triggered by airborne allergens such as pollen. Pollen describes the spores produced by a flowering plant which carry the male gametes. The pollen grains travel through the air to reproduce with other plants. The type of pollen present in the air at any given time is dictated by the flowering season of the native plants.
The symptoms of seasonal allergies are similar to the common cold and include sneezing, runny nose, congestion and itchy eyes and nose. Common seasonal allergens include grasses, trees and weeds.
Drug
A drug allergy occurs when the body’s immune system responds to a component in a medication, either over-the-counter or prescription. Many reactions to medications are not true drug allergies, but are drug sensitivities. The difference is that the allergic reaction involves the immune system whereas a reaction, such as a change in blood pressure, flushing or diarrhea, does not. Examples of drug allergies include penicillin, sulfonamides and some vaccines.
Food
The Food Allergy and Anaphylaxis Network reports that an estimated 12 million Americans suffer from food allergies. A food allergy is triggered by a specific protein found in a food. Although just about any food can trigger an allergic reaction there are eight foods that are responsible for 90 percent of the food allergies, as reported by the American Academy of Allergy, Asthma and Immunology. These include milk, eggs, wheat, soy, peanuts, tree nuts, fish and shellfish. Food allergies can be difficult to live with because it is not as simple as just avoiding the specific food. Labels must be checked to be sure there are no hidden ingredients that can trigger the reaction.
Pet
Contrary to what most people believe, it is not the hair or fur of the pet that usually triggers an allergic reaction. Those allergic to pets or any type of animal experience an allergic reaction to a protein the animal produces and sheds in its skin cells, saliva or urine. The most common trigger of an animal allergy is the skin cells the animal sheds, known as dander. The dander is dangerous because it easily becomes airborne and can remain in the air for long periods of time, according to the Mayo Clinic. Some who are allergic to dogs or cats still choose to live with a pet because they feel the benefits outweigh the inconvenience of the allergies.
About this Author
Stephanie Chandler is a freelance writer whose master’s degree in biomedical science and over 15 years’ experience in the scientific and pharmaceutical professions provide her with the knowledge to contribute to health topics. Chandler has been writing for corporations and small businesses since 1991. In addition to writing scientific papers and procedures, her articles are published on LIVESTRONG.com, eHow, Overstock.com and Helium.com.
