Your first line of defense against disease is the immune system. Your body is well equipped to detect bacteria, viruses, fungi, and other microbial invaders. When these external agents invade, your immune system jumps into action ready to destroy and vanquish. That’s a really good thing… unless the external agent is just a harmless protein.
In simple terms, allergy is the result of your body’s immune system fighting germs that aren’t there. It’s like when you spot a friend at a distance across the mall and rush over to say “Hello” only to find out that it isn’t your friend at all. Allergy is a case of mistaken identity.
“Doctors use the term hypersensitivity to refer to allergies because your immune system is overly sensitive to substances such as pollens, animal dander and oth
er types of allergens that offer no real threat to your health. With hypersensitivity, your immune system acts sort of like an alarm system that summons a SWAT team regardless of whether a cat burglar or just a cat is intruding on your property.”
William E. Berger, MD, MBA
An allergic reaction occurs when your body misidentifies a harmless protein; it over reacts to allergens that pose no real threat. On the first exposure, the misidentification occurs and the immune system creates a special antibody (this is called immunoglobulin E or IgE) designed to fight that substance if it ever sees it again. In a way, it is kind of like how a vaccination works, but instead of being prepared to fight a harmful germ, it is prepared to fight a protein that poses no danger.
The next time you encounter the protein (whether you breathe it, eat it, or it touches your skin) your immune system jumps into action. It produces substances like histamines, leukotrienes, and cytokines. These are the substances that cause you to have sneezing, wheezing, nasal congestion, rashes, coughing, itchy or watery eyes or a runny nose. That’s why the symptoms of allergy can be so similar to the symptoms of a cold.
Your immune system can mistake any protein. The most common indoor allergens come from dust mites, pets, and molds. Outdoor allergens can be the pollen from trees, grasses, and weeds as well as molds and large animals such as horses and sheep. Contact allergens can range from metals to the common ingredients in personal care items. Peanuts, tree nuts, fish and shellfish are also common sources of proteins that cause food allergies.