Allergic hypersensitivity occurs when the immune system over reacts to harmless molecules.

Allergic rhinitis, also called hay fever, affects 16% of people of all ages. The most common symptoms include nasal itching, watery nasal discharge, sneezing, itchy red eyes, sore throat, or hoarse voice.

Allergic rhinitis is caused by a nasal reaction to small airborne particles called allergens (substances that cause an allergic reaction). In some people, these particles also cause reactions in the lungs (asthma), and eyes (allergic conjunctivitis).

Although not life threatening, allergic rhinitis affects the quality of life, sleep, work productivity and school performance.

One of the initial steps in treating any allergic condition is to avoid or minimize exposure to the allergens that cause the condition. Other measures include medication and/or desensitization.

There are four major classes of allergens that trigger allergic rhinitis:

• Pollens (trees, grass, flowers)
• Insects (house dust mites, cockroaches)
• Animal allergens (skin, fur, feathers, saliva)
• Molds

In some cases, it is easy to identify a person’s triggers, based upon when symptoms develop (eg, during a particular season, after exposure to a dog or cat, etc). In people with year-round symptoms, it may be more difficult to pinpoint the allergen(s).

The first step in the treatment of allergic rhinitis is to reduce exposure to allergens. The most common indoor allergens are dust mites and cat and dog dander. However, with indoor allergens, it may take three to six months to see an improvement in symptoms once triggers are removed.

Triggers may be at work home or school. The home is the major source of allergies.

Dust mites are a microscopic type of insect that lives in bedding, sofas, carpets, or any woven material. Dust mites do not bite and do not cause harm to humans, other than by triggering allergies.

They require humidity and feed off organic matter (shed human or animal skin).

The following measures aim to reduce exposure.

Less costly:

• Encase mattress and pillows in allergen-impermeable covers. Finely woven covers for pillows and duvets are preferable.
• Wash bedding weekly in warm water with detergent or use electric dryer on hot setting.
• Reduce indoor humidity to <50% (NB: humidifiers make it worse and should not be used if you have allergic rhinitis)

More costly:

• Remove carpets from the bedroom.
• Replace old upholstered furniture with leather, vinyl, or wood.

The allergic component is dead skin, hair and saliva. Any breed of dog or cat can be allergenic. Cats tend to be more allergenic than dogs. Birds also can be allergenic.

If a person is found to be allergic to a pet, the most effective option is to remove the pet from the home. Limiting an animal to a certain area in the house is not effective because allergens are carried on clothing or spread in the air.

Once a pet has left a home, careful cleaning (or removal) of carpets, sofas, curtain, and bedding must follow.

If it is not possible to remove the animal, measures can be taken to decrease exposure to the animal dander, although none of these methods is as effective as removing the animal. Vacuum cleaners with a HEPA filter are effective in reducing cat and dog allergen levels in the home and can reduce symptoms. Or keep the pet in a room with a HEPA filter and replace the filter as recommended by the manufacturer.

Cockroach droppings contain allergens that can trigger asthma and allergic rhinitis in sensitive individuals. Cockroaches thrive in warm, moist environments with easily accessible food and water.

Certain measures are recommended, including:

• Use multiple baited traps or poisons
• Remove garbage and food waste promptly from the home
• Wash dishes and cooking utensils immediately after use
• Remove cockroach debris quickly
• Eliminate any standing water from leaking taps or drains
• Keep humidity levels less than 50 percent with a dehumidifier or air conditioner
• Consult a professional exterminator for large or recurrent infestations

Allergies are caused by protein in the urine of mice and rats.

To reduce rodent allergens significantly:

• Consult a professional exterminator.
• Periodically clean home thoroughly.
• All food should be stored in sealed containers. Do not store garbage inside.
• Repair holes in walls, doors, floors, and block other entry points.

Mold spores are present all year round and trigger allergic rhinitis in allergic patients. Mold allergies are problematic because they grow invisibly anywhere in the house, where it is damp as well as in soil and moldy food.

Area such as air conditioning vents, refrigerator drip trays, shower stalls, leaky sinks and porous roofs (dark staining on the ceiling) are particularly vulnerable to mold growth if not cleaned regularly.

Elimination of potential sources of mold include:

• Cleaning moldy surfaces with dilute bleach solution.
• Fixing water leaks.
• Reducing indoor humidity to <50 percent. Avoid use of humidifiers.

Air filtration devices, including HEPA filters, other mechanical filters, and electrostatic filters are frequently recommended as a component of environmental control practices for patients with allergic respiratory disease.

The efficacy of air filtration devices is mixed with some studies showing clinical benefit and others showing minimal improvement.