Allergy is an exaggerated immune system response to a harmless substance that does not affect most people. Common allergens (the name given to these trigger substances) include pollen, mold, dust mites, pet dander, food and chemicals. Allergies can cause cold-like symptoms or skin rash.

Understanding the Immune System

The immune system is the 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 substance that doesn’t actually cause harm. 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.

Allergy Types and Treatments

Allergies may be seasonal or occur year-round. Hay fever 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, too. They can produce a life-threatening allergic reaction known as anaphylaxis.

Ideally, the best way to prevent allergies is to avoid the allergen responsible for your symptoms, but this is often a challenge. Medications such as antihistamines, decongestants and corticosteroids usually provide relief from symptoms. Immunotherapy, or allergy shots, is an effective long-term solution for those whose allergies don’t respond to medical treatment.