Hay fever is an allergic reaction that may occur seasonally or year-round. Hay fever symptoms in the spring and fall of the year may be caused by inhalation of allergens such as pollen or mold spores. Pet dander and dust mites sometimes trigger year-round hay fever symptoms. Contrary to its name, hay fever is not usually caused by exposure to hay, and its symptoms do not include a fever. Hay fever causes symptoms that may affect the eyes, ears, and nose of an affected person.
Hay fever may result when a person inhales an airborne substance called an allergen. Allergens enter the body through the mouth, nose, throat, and lungs. They are not usually harmful, but once they are inside the body, the immune system may identify them as dangerous and produce antibodies to attack them. The next time a person inhales the same allergen, the immune system may recognize it and begin to produce a chemical called histamine to counteract the allergen.
When histamine gets into the bloodstream, it can cause inflammation. This inflammation results in the symptoms of hay fever, which can include itchy, watery eyes, coughing and sneezing. Other symptoms include sinus pressure and a decreased ability to smell and taste. A person suffering from hay fever may also suffer from fatigue and feel like their ears are plugged.
Those who have hay fever may experience increased symptoms in the spring and fall of the year, when plants release pollen, or "pollinate." Pollination may depend on the local climate, the amount of rainfall, and the type of plant. Plant pollens that commonly cause hay fever in the spring include the particles released by grasses, trees, and certain types of weeds, especially ragweed. Approximately 75 percent of those who suffer from allergies are estimated to be allergic to ragweed. Some weeds also may release pollen in the fall.
Mold is one of the most common hay fever causes. It is often present indoors and outdoors at all times of the year. Mold thrives indoors in damp environments like basements and bathrooms and outdoors in moist conditions such as compost piles. Mold produces "spores," which are present in the air, contained in water, or carried by insects. If these spores enter the body, they may trigger an allergic reaction such as hay fever.
Dust mites may also be common hay fever causes. Dust mites are microscopic, spider-like creatures that are present in household dust, carpeting, and bedding. They typically feed on dead skin cells and cause hay fever symptoms when they invade the body. There may be no way to completely eliminate dust mites, but they can be controlled by reducing humidity in the home and by washing bedding in hot water.
Pet dander is flaky dry skin visible on the fur of cats and dogs and the feathers of birds. Pet dander resulting in hay fever causes symptoms including sneezing, runny nose, and itchy eyes. The hair or feathers alone is not believed to be the cause of the irritation. Rather, the pollen, mold, and dust particles that collect on the pet's fur or feathers are believed to trigger the allergic reaction.
Pet dander can also be carried to a location where the pet has never been, sometimes being transported on the clothing of a person exposed to the pet. This may cause pet allergies and hay fever symptoms in an individual who has never been around a pet. Pet dander may remain in a home up to six months after the animal has been removed.
