What causes allergic rhinitis (hay fever)?

What causes allergic rhinitis (hay fever)?

Allergic rhinitis occurs when your body’s immune system reacts to an irritant in the air. The irritants (allergens) are so tiny that you can easily inhale them through your nose or mouth.

Allergens are harmless to most people. But if you have hay fever, your immune system thinks the allergen is intruding. The immune system tries to protect your body by releasing natural chemicals into your bloodstream. The main chemical is called histamine. It causes mucous membranes in the nose, eyes and throat to become inflamed and itchy as they work to eject the allergen.

Seasonal and perennial allergies can result from many allergens, including:

• Dust mites that live in carpets, drapes, bedding and furniture.
• Pollen from trees, grass and weeds.
• Pet dander (tiny flakes of dead skin).
• Mold spores.
• Cockroaches, including their saliva and waste.

Food allergies can also cause inflammation in the nose and throat. If you think you’re having an allergic reaction to something you ate, get medical help right away. Food allergies can be life-threatening.