Asthma Triggers During the Fall and Winter

by Frederic Little, M.D. Health Professional

In this entry, I would like to discuss how individuals with asthma are affected in the cold months of the year. While most of this applies to those who live in temperate climates with cold winters, the indoor triggers that can lead to more asthma symptoms will affect asthmatics in tropical climates as well.

Main indoor asthma triggers
In northern climates, we spend much more time indoors in fall and winter than in the spring and summer. This means that if there are asthma triggers indoors, we are getting more exposed to them. As many of these are in the air and windows are closed when it is cold, air circulation or "replacement" is decreased.

In past entries, I have commented on the relationship between allergies and asthma. For many asthmatics, their hay fever is associated with their asthma - the triggers that worsen nasal congestion, sneezing, and runny nose also trigger asthma. In the warm months, the primary triggers are plant pollens. In the spring, tree pollens are prominent. The tree pollen that coats your car and driveway in yellow 'dust' (primarily pine pollen) is not the kind that triggers your allergens. Instead, small, light, dry pollens such as the pollen of oak, elm, birch, ash, hickory, poplar, sycamore, maple, cypress and walnut trees triggers allergies. The main pollens in the summer are grass pollens (such as timothy, Bermuda and red top grasses), and in the fall, up until the first frost: ragweed pollen.

The main airborne allergens in the cold months are indoors - pets (primarily cats and dogs), pests, and dust/dust mites. Cats can be especially problematic because they are "vertical" as well as "horizontal" pets - they like to climb on furniture, sit on top of the (warm) TV or VCR, and therefore tend to lead to higher airborne allergen levels that dogs. Pests include rodents (both rats and mice) as well as cockroaches. House dust mites live in our mattresses, box springs, and upholstered furniture, surviving on flecks of skin that we normally shed as part of normal skin maintenance. These potential allergens are common triggers for many individuals with asthma and/or allergies. As noted above, they are relevant year round, but for those who are sensitive, they are the major triggers during the cold months when we spend more time at indoors.

Tips on controlling triggers

  • A first step in controlling exposure to indoor allergen triggers is finding out what you are allergic to. If asthma and allergy symptoms are significant during the cold months, you can speak with your doctor about allergy testing. This can be carried out with blood or skin testing (I will discuss these tests in more detail in a later entry).

  • There are some indoor allergens whose presence we can control. These include pets and pests, primarily. If a favorite pet is causing significant asthma symptoms, then there are careful (and difficult) decisions to make. Removing a "culprit" pet from the household is the best way - limiting a pet to certain parts of the house doesn't work as well, as other people and objects (e.g. clothes) come into contact with the pet which can transport the allergen to the restricted areas, typically the bedroom.

  • Another important fact is that after removing a cat from a household, it can take up to 3 months for cat allergen levels to clear. This can be somewhat helped with deep cleaning after the cat has left.

  • With regard to rodents and cockroaches, it is recommended to have an exterminator assist with pest control. If you are a tenant and your symptoms are clearly related to pests (as determined by your doctor with a careful symptom log and allergy testing), you can ask your doctor to write a letter on your behalf that emphasizes the importance of pest eradication in your apartment.

  • It is harder to control the presence of house dust mites. The best way to control exposure is to cover mattresses, box springs, and pillows with airtight dust mite covers. Many brands are readily available commercially and they are reasonably priced, typically for less than $75. These covers serve two purposes: they separate you from the dust mites and "starve" the mites living in your mattress as they live off of small flecks of skin that we shed.

  • In addition to covers, all bedding (including pillowcases) should be washed in hot water weekly. Dust mites can also live in carpets and upholstered furniture. We recommend avoiding wall-to-wall carpeting; small area rugs are better and no rugs at all is best. Vinyl or leather furniture is preferred over upholstered furniture as it is difficult to cover upholstered furniture without feeling like you are trying to relax on a shower curtainClosing thoughts
    As with most asthma triggers, controlling trigger exposure in the cold months of the year is key to improving asthma control. You should discuss detailed strategies that apply to you personally with your asthma care provider.

Frederic Little, M.D.
Meet Our Writer
Frederic Little, M.D.

Frederic Little is an Assistant Professor in the Department of Medicine at Boston University. He attends on the Allergy Consultation Service as well as the Medical Intensive Care Unit and Pulmonary Consultation Service at Boston Medical Center. He wrote for HealthCentral as a health professional for Asthma and Allergy.