An allergy is an exaggerated response from your immune system to a normally harmless substance. Common allergens (the name given to these trigger substances) include pollen, mold, dust mites, pet dander, food and chemicals. Allergies affect about one out of every five Americans.
Cause
Your immune system is your body’s first line of defense against germs and bacteria. 
Comprised of cells, proteins, tissues and organs, it is essential in maintaining your health and preventing infections. When a threat is perceived, the immune system responds by attacking the substances that are invading the body.
Allergies are the result of the immune system responding in an overprotective manner to a normally harmless substance. When an allergen is encountered, antibodies – proteins designed to protect against foreign invaders – are produced. These trigger the release of chemicals called histamines, which are responsible for the telltale symptoms of allergies: swelling, inflammation, itching and mucus production.
Symptoms
Allergies may be seasonal or occur year-round. Hay fever, also called allergic rhinitis, is caused by pollen from grasses, trees and weeds is the most common seasonal allergy. Symptoms include stuffy and/or runny nose, sneezing, itchiness in the nose and throat, postnasal drip, itchy and watery eyes, pressure in the ears and fatigue. Year-round allergies produce the same symptoms; common ones are mold, dust mites, pet dander, environmental irritants, like smog or smoke, medications and chemicals. Insect stings and bites fall in this category. They can sometimes produce a life-threatening allergic reaction known as anaphylaxis. Allergies to foods can also cause rashes, asthma, swelling and even anaphylaxis.
Treatments
Avoiding the allergen trigger is the best method of preventing allergy attacks. Medications are available to reduce your immune system’s reaction and provide symptom relief; drugs such as antihistamines, decongestants, and corticosteroids can all prove helpful. Those whose allergies do not respond to medical treatment may be given allergy shots (immunotherapy) in an effort to build up a tolerance to the offending substance through regular injections given for several years.
Call The Allergy Center at Sacramento Ear, Nose & Throat at (916) 736-6644 for more information or to schedule an appointment