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Environmental Control

Ignoring exposure levels may cause treatment failure despite medications and immunotherapy. On the other hand, one can easily waste considerable time and money on unnecessary and inappropriate measures. This section doesn't cover everything you need to know, but I hope it motivates you to do further research.

Basic Information:

What is an allergen?

A protein triggering an immune response causing sneezing, congestion, runny nose, asthma and other symptoms. These are from weeds, trees, grasses, molds, pet dander and others such as dust mites.

What is a non-allergic trigger?

Irritants and non-protein materials can set off an allergic-like reaction. Examples are strong chemicals such as formaldehyde, gasoline, perfumes, cleaning materials and cigarette smoke.

How do I treat non-allergic triggers?

Avoidance and medications but not immunotherapy are used fro non- allergic issues.

"I am allergic to everything, so I can't do avoidance measures."

This simply isn't true. While total avoidance is impossible, limiting frequency and amount of exposures is beneficial.

You have a level of tolerance to all allergens. The "total load" is the sum of all exposures and when it exceeds your tolerance, you have symptoms. The goal is to reduce the total load.

Allergic patients have greater sensitivity to non-allergic triggers. Reducing irritant exposures will improve your symptoms. Similarly, if you control allergies (with medications and immunotherapy), you will have less severe reactions to irritants.

Now let's look at the different environments for allergen exposure and the best methods for control.

Indoor Allergens

Most environmental control measures are aimed at indoor allergens such as dust mites, pet dander, cockroaches and molds.

In your home, the bedroom should be the focus of your efforts as this is where you spend the majority of time. Other problem areas include damp basements, bathrooms and in areas with current or past water damage.

The indoor air quality is composed of a wide range of irritants including traditional allergens (pet dander, mold, dust mites), chemicals (formaldehyde, other petrochemicals), and dangerous toxins (radon). Each one of these can serve as a trigger.

1. Pets:

Cats are some of the most difficult allergens to control. I call cats the nuclear material of the allergy world. It's not that I don't like cats, it's because their antigens are lightweight and stable for a long time. You stir up cat dander just by walking through a room and moderate levels can still be detected years after the cat has been removed. In addition, cat dander can stick to materials. A new mattress in a store will show high levels of cat antigen within two weeks just from people with cats "testing it out". I have even seen symptoms arise just from being around people who have cats.

I strongly recommend for indoor cats to be excluded from your bedroom at all times. I do not recommend bathing a cat as the antigen is in their saliva, and the first thing a cat does after bathing is lick its fur.

Dogs are also antigenic, but not much as cats. Attempts have been made to breed non-antigenic cats and dogs with some success. Unfortunately, they're very expensive (thousands of dollars) and difficult to find.

The length of the animal's hair is probably not very important and there is no good evidence to support the claims of certain breeds of dogs being beneficial for asthmatics.

Studies do vary in whether early exposure to pets in infancy increases or decreases the risk for sensitivities. I would recommend using common sense. If a child shows significant allergies early on, limit additional exposures such as pets as much as possible.

2. Dust mites:

Dust mites are microscopic insects feeding on shed skin cells found in mattresses, upholstered furniture, carpet and stuffed animals. They require 50% humidity to survive and are not found at high altitudes such as in Denver, Colorado (unfortunately they are in Denver, NC).

Control methods include dehumidifiers to maintain levels at 45%, covers for mattresses and pillowcases, and HEPA filter vacuums. Sprays to apply to carpet can be useful but require repeated use. Stuffed animals can be frozen to kill dust mites and then "fluffed" in the drier to remove debris. Since dust mites do not fly, air filtration systems are of no benefit.

Keeping your bedrooms as free as possible of carpeting, upholstered furniture and stuffed animals limits the possible "load" of dust mites in a room. Sheets should be washed weekly in hot water as well.

3. Dust:

Dust is composed of dirt, fibers, insect debris, and food particles unique to every home. Evidence suggests "old" house dust is more irritating than "new" dust. The only control method is general cleaning. It is best to have someone other than the patient to do this. Masks are somewhat beneficial, but can't be relied on for complete protection. When heavy exposure is expected, you can pretreat with medications such as antihistamines and nasal steroids. Some studies suggest saline gels applied in the nose will trap pollens and irritants and prevent them from contacting the nasal lining. Saline nasal sprays or rinses during and after exposures may be beneficial.

Air filters and cleaners are also useful, but probably overemphasized in their importance. Ozone generating air purifiers are best avoided and potentially dangerous.

4. Indoor Molds:

Water and food (organic material) are the two essential elements for mold growth. Removing the water source is the most important technique to controlling molds. Dehumidification, restoring drainage or eliminating damp, wet materials is critical to success. Bleach and other cleaning agents will kill visible molds but it will recur quickly if the water supply isn't eliminated.

To fix basement and crawl space moisture problems may require installing proper drainage away from the house. Water leaks soaking carpet and pads may need replacement or at least extensive drying. I never recommend cleaning up large mold problems yourself. Enlist professionals for this work. Even minor manipulation can aerosolize molds and cause severe pulmonary disorders and even death.

Mold testing in the home is a "tricky" business. I do not believe that random air samples demonstrating molds is adequate to define the problem. Generally a source of the mold must be found, tested and addressed. Room dehumidifiers are of benefit, but must be cleaned and maintained to prevent them from become another potential source of the problem. Entire home dehumidifiers are less effective.

5. Cockroaches:

Cockroaches are everywhere, but they are more prevalent in older buildings and large urban areas. Cockroach allergens have been associated with asthma. Eliminating food and water sources and are critical to controlling cockroach populations.

6. Irritants and Toxins:

While not technically allergies, the reactions are similar and control is important.

The Environmental Protection Agency (EPA) maintains a very nice website outlining many issues regarding indoor air quality. (EPA website, Radon EPA website In addition I recommend a blog specifically about this tissues:

Outdoor allergens:

The offending outdoor pollens are trees in the spring, grasses in summer and weeds in the fall. I often hear patients say "I have a lot of trees in my yard I am allergic to, should I cut them down?" The answer is "no". These pollens are in the air and dispersed widely, so you won't make much difference by cutting down a few trees.

I don't like advice of "stay inside" as this is not practical. I do think that you can choose times to be outside especially for exercise.

It can be important to know at what times of the day pollen and mold counts are highest. You can try and avoid exercising or working outside at these peak hours.


Environmental control continues to be an evolving area of allergy care. I recommend you do your own research and do not necessarily rely on one source. So much of the information out there is biased and motivated by selling a product or service. Be informed. Be skeptical, and be cautious. Spending more money doesn't correlated to better results.