Hay fever, also known as allergic rhinitis, is an allergic response to pollen (the male component of the plant reproductive system), mold (a type of fungus that is usually found in the outdoor environment and in damp, dark indoor areas like the basement or bathroom), or other microscopic substances. Hay fever can be either seasonal or perennial (year-round). Seasonal hay fever occurs when particular plants or trees produce pollen, which is released into the air to fertilize the eggs of that plant or tree.

In the spring, pollinating trees are responsible for causing hay fever. Over the summer, grasses and weeds produce the pollen. And in the fall, ragweed is usually the culprit. Hay fever can also be caused by fungus releasing its reproductive cells, called spores, from late March until November.

Year-round hay fever 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 Hay Fever?

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, itching, and a runny nose.

People with hay fever have sudden sneezing, a watery nasal discharge, puffy eyes, and fatigue. Symptoms can occur at all stages of life, but most people develop hay fever before reaching 30 years of age.

How Do I Find Out What Causes My Hay Fever?

The season in which your allergy occurs 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.

If skin testing cannot be performed, the doctor may perform a radioallergosorbent blood test (RAST) to check the levels of antibodies produced by the immune system. Elevated levels of certain antibodies can identify particular allergies. Because RAST is not as sensitive as skin testing in detecting certain substances, it is only used when skin testing isn't possible.

Why Do Only Some People Get Hay Fever?

Hay fever affects 10% to 20% of the U.S. population and is the most common allergy 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 is hereditary (passed on from parents to children). People who suffer from asthma or eczema are also more likely to develop hay fever.

Why Is My Hay Fever Better on Some Days and Worse on Others?

While the pollen seasons for particular plants are very consistent within each geographical region, the weather plays a large role in determining how heavy the pollen count will be, both seasonally and daily. Usually, pollen counts are highest on warm, dry, and breezy mornings and lowest on rainy, cooler days. The severity of your allergic reaction will generally mirror the rise and fall of the pollen count.

How Is Hay Fever Treated?

The most effective treatment is simply to avoid the allergen. Air conditioner filters remove 99% of airborne pollen. Facemasks, similar to those worn by surgeons, can significantly reduce the amount of allergen you inhale while outdoors.

If you have eye allergies, try wearing wraparound or goggle-type sunglasses to protect your eyes from pollens. If you are exposed to pollen, wash your eyes and your eyeglasses frequently with soap and water. Use cool compresses to relieve eye symptoms. Ask your doctor about over-the-counter and prescription drugs that can provide relief.

Effective drug therapies for hay fever include antihistamines that block the chemical that causes symptoms, cromolyn which prevents the mast cells (a type of blood cell) from releasing histamine, and topical nasal steroids that decrease swelling and inflammation.

Antihistamines: Nonprescription antihistamines such as Benadryl or Chlor-Trimeton are generally effective for treating mild cases of hay fever. Antihistamines don't prevent the release of histamine, but they do prevent some of the chain reactions triggered by histamine, which in turn reduces symptoms. But antihistamines can cause drowsiness. They should not be taken when driving a car, drinking alcohol, or while taking other drugs that cause drowsiness. However, the prescription antihistamines Allegra, Claritin, and Clarinex do not cause drowsiness. Astelin is an antihistamine in nasal spray form that is now available to treat the symptoms of hay fever.

Decongestants: Over-the-counter decongestants (either pills, drops, or sprays), such as Neo-Synephrine and Sudafed, help unblock nasal passages and improve breathing. But a note of caution: Over-the-counter nasal sprays or drops can, after a few days, start to have the opposite effect and may make congestion worse; they can also become addictive.

Cromolyn: This drug inhibits one of the cell types involved in the allergic reaction. The over-the-counter form of this medication is Nasalcrom. Unlike some other medicines, the effects of cromolyn take approximately two weeks to be felt. On the plus side, it is used for long-term treatment and has few side effects.

Steroid nasal sprays: Prescription nasal sprays such as Rhinocort, Beconase, Flonase, Vancenase, Nasonex, and Nasalide can effectively limit reactions to allergens.

Saline nose sprays: Salt water, saline nose sprays help clean out allergens caught in the nasal passages and keep the passages moist.

Eye drops: All of the medicines mentioned above also come in eye-drop form to relieve allergy-related eye problems (also see Allergic Conjunctivitis).

Before using any over-the-counter drugs, make sure you discuss with your doctor how they may affect other medicines you may be taking.

Will Allergy Shots Help My Hay Fever?

Immunotherapy, also known as allergy shots, is a treatment method designed to increase your tolerance to the substances that trigger your symptoms. They won't cure your allergies, but they'll reduce your sensitivity to certain substances. The allergen is injected periodically into your upper arm at increasingly larger doses. The injections continue until your body builds the production of antibodies and your immune system no longer considers the allergen an invading agent; this usually takes three to five years.

Allergy shots have shown positive results in people with extreme hay fever and are usually recommended for people who suffer from allergies more than three months each year.

Reviewed by the doctors at The Cleveland Clinic Department of Pulmonary, Allergy and Critical Care Medicine.

Edited by Charlotte E. Grayson, MD, Feb. 2004, WebMD.

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