According to the Mayo Clinic, about one in five people experiences allergic rhinitis, or hay fever--an allergic reaction to airborne allergens--and many of these cases are considered seasonal allergies. The allergens grow only at certain times of the year. Allergies to pet dander and dust mites cause similar symptoms, although they are not considered seasonal allergies.
Causes
Seasonal allergies are usually caused by pollen or mold spores. The particles that cause the allergic reaction are typically too small to see and include pollen from trees, grasses or ragweed. Different people react to different allergens, and one person's hay fever trigger may cause no effect in someone else. A given individual may also be allergic to more than one type of pollen or spore, and these may be allergens that are released into the air at the same time or during different seasons of the year. Most plants and molds that produce allergens release them in the spring and fall, making these the most common times for seasonal allergies.
Biology
The immune system reacts to seasonal allergens as though they are invaders, treating them similarly to bacteria or a virus. When an allergen particle is inhaled, the body produces an overabundance of histamines. Histamines are chemicals released by the immune system that dilate blood vessels and make cells more permeable to proteins in order to help the immune system rapidly fight an infection. The inflammatory response of the body to the presence of too many histamines causes allergy symptoms. The symptoms, therefore, are produced by the immune reaction and are not an effect of the allergen itself.
Symptoms
The symptoms of a seasonal allergy depend on an individual's immune reaction to the allergen and the level of allergens in the air on a given day. Typically, most seasonal allergy sufferers experience one or more of the following: itchy nose, throat or eyes, sneezing, congestion, runny nose, watery eyes, difficulty smelling, headache, coughing, sore throat, fatigue, bloodshot eyes and puffiness under the eyes.
Treatment
Reducing exposure helps avoid the symptoms of seasonal allergies, but this isn't always possible. Allergy sufferers may try medications that will help tone down the body's response to allergens or treat the symptoms of the allergy. These include antihistamines, corticosteroids, decongestants and nasal saline sprays. People who have severe symptoms may try immunotherapy, the administration of allergy shots to try to slowly build up tolerance to the allergen.
Considerations
People with seasonal allergies may want to pay attention to the pollen count, which usually can be found listed in the newspaper, announced on local television weather reports or found on the internet. The pollen count tells how much pollen and other allergens are expected to be in the air that day, giving allergy sufferers a heads-up on whether or not they should expect symptoms. Knowing the pollen count in advance allows allergic individuals to plan ahead and take antihistamines as a protective measure on days when there will be a lot of allergens in the environment. Some individuals also find that if they move to a different climate their allergies disappear, since the original plant or mold that caused the allergy doesn't exist in the new location.
