Allergies and Hay Fever

Seasonal allergic rhinitis, sometimes known as hay fever or simply allergies, is an allergic response to pollen (the male component of the plant reproductive system) or other microscopic substances that are present only at certain times of the year. Allergic rhinitis can also be perennial (year-round).

In the spring, pollinating trees are responsible for causing allergic rhinitis. Over the summer, grasses and weeds produce the pollen. And in the fall weeds are mostly to blame, with ragweed being the main culprit. Allergic rhinitis can also be caused by mold releasing its reproductive cells, called spores, from late March until November, usually peaking in late summer and early fall.

Perennial allergic rhinitis is caused by agents that are present throughout the year, such as dust mites, mold, animal dander, and feathers. These irritants can be found in pillows, down clothing, draperies, upholstery, thick carpeting, and bedding.

It is common for people to be allergic to more than one pollen or agent.

What Are the Symptoms of Allergic Rhinitis?

In cases of allergic rhinitis, your body's immune system interprets the allergen (pollen, mold, dander, etc.) as an "invader" and responds by releasing a chemical called histamine into the bloodstream.

Histamine causes inflammation (swelling and redness) of the sinuses, nose, and mucus membranes of the eyes and triggers sneezing. The swelling reaction is designed to block the allergen from entering the body and sneezing is a method to expel it out of the body. Histamine also allows fluids to enter the nasal tissue, resulting in congestion and an itchy, runny nose.

People with allergic rhinitis have sudden sneezing and a watery nasal discharge. Symptoms can occur at all stages of life, but most people develop them before reaching 30 years of age.

How Do I Find Out What Causes My Allergies?

The season in which your allergies occur will narrow the list of possible culprits. To pinpoint the cause, your doctor may perform a skin test to determine which substances (allergens) cause a reaction.

The skin test involves placing extracts of potential allergens in a grid on your arm or back, and then pricking your skin so the extract can enter the outer layer of skin (epidermis). Those areas that become red and itchy indicate which substances trigger a defensive (allergic) response by your immune system.

Your doctor may also perform a blood test to check the levels of antibodies produced by the immune system. Elevated levels of certain antibodies can identify particular allergies.

Why Do Some People Only Get Seasonal Allergies/Hay Fever?

Hay fever affects 10% to 20% of the U.S. population and is the most common allergic response in the country. It is unknown why some people get allergies while others do not. However, there is some evidence to suggest that hay fever and other types of allergies are hereditary (passed on from parents to children). People who suffer from asthma or eczema are also more likely to develop hay fever or perennial (year-round) allergic rhinitis.