If you have questions about hay fever, you're not alone. Seasonal allergies are one of the most common allergic conditions in the U.S., affecting nearly 36 million people each year.

Is hay fever caused by an allergic reaction to hay?

Hay fever is definitely a misnomer! Hay almost never triggers it and it doesn't cause a fever. Allergic rhinitis, the medical name for hay fever, is caused by an allergic response to allergens, such as pollen, dust mites, or pet dander.

If I have a runny nose, does it mean I have hay fever?

According to the American Academy Allergy Asthma & Immunology, at least one-third of people with nasal symptoms do not have allergies. Viruses, bacterial infections, and irritants such as smoke or cleaning solutions can lead to nasal symptoms, but are not an allergic response.

What triggers allergies in some people—but not others?

In allergic individuals, the immune system mistakenly identifies a harmless airborne substance as harmful and produces antibodies to it. The next time the person encounters that substance, the antibodies recognize it and signal the immune system to release chemicals, such as histamine, into the bloodstream, causing a reaction that leads to symptoms.

What are the most common allergy triggers?

Among pollens, ragweed is the most common allergy, followed by timothy grass, then maple, oak, and cottonwood trees, says Karen Calhoun, MD, from the Department of Otolaryngology at the Ohio State University Wexner Medical Center. She estimates that 70 percent of her patients are allergic to at least one type of tree and about 50 percent to at least one type of grass. That extends allergy season for a lot of people. Trees pollinate in the spring, grasses in the summer, and weeds in the fall. Other common hay feed triggers include dust mites, pet dander, molds, and fungi.

I'm an adult and have never had allergies—until now. What's going on?

Individuals are most likely to develop allergies during childhood or early adulthood, but can develop allergies at any age. Calhoun tells adult patients they likely had a tendency to allergies since childhood, but the symptoms were mild enough not to be noticeable. Then something changes, such as their geographic location, home or work environment, stress levels, or other conditions and the symptoms cross the threshold and become troublesome.

What makes my nose run?

Rhinorrhea or rhinitis, more commonly known as a runny nose, is excess drainage produced by tissues and blood vessels in the nasal passage. Anything that irritates or inflames nasal tissues (cold, influenza, allergies) may cause a runny nose. You may suffer from a runny nose with or without nasal congestion (trouble breathing through the nose).

Karen Calhoun, MD, reviewed this article.




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