A condition in which the immune system reacts abnormally to a foreign substance. An allergy is an immune system response to a foreign substance that’s not typically harmful to your body. These foreign substances are called allergens. They can include certain foods, pollen, or pet dander. Your immune system’s job is to keep you healthy by fighting harmful pathogens.

A condition in which the immune system reacts abnormally to a foreign substance. An allergy is an immune system response to a foreign substance that’s not typically harmful to your body. These foreign substances are called allergens. They can include certain foods, pollen, or pet dander. Your immune system’s job is to keep you healthy by fighting harmful pathogens.

Common symptoms of allergic rhinitis are sneezing, nasal itching, running nose, nasal congestion or stuffiness, cough, facial pressure or pain, or headache. The allergens may also affect the eyes, causing watery, reddened, puffy or itchy eyes.
Doctors don’t know why some people experience allergies. Allergies appear to run in families and can be inherited. If you have a close family member who has allergies, you’re at greater risk for developing allergies. Although the reasons why allergies develop aren’t known, there are some substances that commonly cause an allergic reaction. People who have allergies are typically allergic to one or more of the following:
  • pet dander
  • bee stings or bites from other insects
  • certain foods, including nuts or shellfish
  • certain medications, such as penicillin or aspirin
  • certain plants
  • pollen or molds