Prevention

People with existing allergies should avoid irritants or allergens. These triggers include:

  • Pollen. This is the primary cause of allergic rhinitis.
  • Dust mites, specifically mite feces, which are coated with enzymes that contain a powerful allergen. These are the primary allergens inside the home.
  • Animal dander (flakes of skin) and hair from cats, house mice, and dogs. House mice are proving to be significant sources of allergens, particularly in urban children.
  • Molds.
  • Fungi.
  • Cockroaches are major asthma triggers and may reduce lung function even in people without a history of asthma.
  • Some research suggests that alcohol intake may influence allergy severity. One study found that as little as one drink a day is enough to worsen dust mite allergies.
  • Some studies suggest that early exposure to some of these allergens, including dust mites and pets, may actually  prevent allergies from developing in children.

Indoor Protection Against Allergens

Some experts believe that reducing the risk factors for asthma in the home could reduce asthma in children by as much 40%.

Controlling Pets. People with asthma who already have pets and are not allergic to them are probably at low risk for developing such allergies later on. When children are exposed to more than one dog or cat during their first year, they have a much lower risk for not only pet allergies but also seasonal allergies and asthma. (Pet exposure does not protect them from other allergens, notably dust mites and cockroaches).

In children who have an existing allergy to pets, however, the pets should be given away or kept outside. If this isn't possible, they should at least be confined to carpet-free areas outside the bedroom. Cats harbor significant allergens, which can even be carried on clothing. Dogs usually present fewer problems. Washing animals once a week can reduce allergens. Dry shampoos, such as Allerpet, that remove allergens from skin and fur and are now available for both cats and dogs and are easier to use than wet shampoos.

For small children, stuffed animals might serve as a comforting replacement, although they might harbor dust mites. Putting stuffed animals in the freezer for 24 hours before washing them kills the dust mites. For best effect, this process should be done weekly.

Preventing Exposure to Cigarette and Cooking Smoke. Parents who smoke should quit. Studies show that exposure to second-hand smoke in the home increases the risk for asthma and asthma-related emergency room visits in children. Even smoky cooking can worsen asthma. [For help in quitting, see In-Depth Report # 41: Smoking.]

Controlling Dust. Spray furniture polish is very effective for reducing both dust and allergens. Air cleaners, filters for air conditioners, and vacuum cleaners with High Efficiency Particulate Air (HEPA) filters can help remove particles and small allergens found indoors. Neither vacuuming nor the use of anti-mite carpet shampoo, however, is effective in removing mites in house dust. Vacuuming actually stirs up both mites and cat allergens. People with these types of allergies should avoid having carpets or rugs in their homes.

Bedding and Curtains. Many experts recommend reducing exposure to dust mites by enclosing mattresses and pillows in semipermeable coverings. (Vinyl mattress covers limit airflow and may worsen, or even cause, asthma in children.) However, several 2005 studies suggested that such covers do not prevent allergies or asthma. Curtains should be replaced with shades or blinds and bedding washed using the highest water temperature setting.

Reducing Humidity in the House. Although warm, moist air from vaporizers can greatly ease and moderate asthma attacks, living in a damp house is counterproductive. Dust mites thrive in humidity, and damp houses increase the risk for mold. On-going humidifiers can worsen the problem. If they are used, humidity levels should not exceed 40%, and humidifiers should be cleaned daily with a vinegar solution.

Exterminating Pests (Cockroaches and Mice). Use professional exterminators to eliminate cockroaches. (One study reported that ridding a home of cockroaches and cleaning the house using standard housecleaning techniques failed to eliminate the cockroach allergens themselves.) Exterminate mice and attempt to remove all dust, which might contain mouse urine and dander.

Outdoor Protection

Avoiding Outdoor Allergens. The following are some recommendations for avoiding allergens outside:

  • Start taking allergy medications 1 or 2 weeks before ragweed season begins. Be sure to take allergy medications before going outside. If regular medications do not work, ask your doctor about allergy shots.
  • Camping and hiking trips should not be scheduled during times of high pollen count (May and June for grass pollen and September to October for ragweed).
  • Patients who are allergic should avoid barns, hay, raking leaves, and mowing grass. (A mask can be worn during outdoor chores to help reduce pollen exposure.)
  • Sunglasses can help prevent pollen from getting into eyes.
  • After being outdoors, clean off pollen residue by bathing, washing hair and clothes, and using a nasal salt water rinse.

Dietary Factors

Some evidence suggests that people with allergic rhinitis and asthma may benefit from a diet rich in omega-3 fatty acids (found in fish, almonds, walnuts, pumpkin, and flax seeds) and fruits and vegetables (at least five servings a day). Some studies also suggest reducing sodium, transfatty acids (hydrogenated fats found in commercial products and baked goods), and omega-6 fatty acids (found in most vegetable oils). Investigators are also studying probiotics -- so-called good bacteria, such as lactobacillus and bifidobacterium, which can be obtained in supplements.