When you were a young asthmatic child and got a bad cold with wheezing and coughing, did your mom put you in a bathroom with hot steam from the shower and set up the humidifier in your room? Although your mom was well-intentioned, it probably wasn’t the best idea. Don’t be too hard on her—the pediatrician probably told her to do it. For years health professionals thought that high humidity was helpful in treating asthma attacks. As it turns out, not only is high humidity not generally helpful, it may actually make asthma worse.

Steam and humidifiers work for upper airway inflammation, or croup, but does not work for inflammation in the lungs, or the lower respiratory system. How does a mom tell the difference? It’s not always easy. Children with croup have a barky cough and stridor, or a harsh wheezing sound when breathing in or out. The wheeze of an asthmatic child is usually a tight squeaky sound when the child breathes out.

Many studies have been down that demonstrate the relationship between humidity and asthma. In one study by Hare and Buchdahl, areas of the world that have a humidity rate of less than 50% also have a lower rate of asthma. They estimated that for every 10% rise in humidity, there was a 2.7% rise in the incidence of asthma (www.ace.mmu.ac.uk/Newsletter/0704.pdf).

Why is it that high humidity is difficult for asthmatics? Several possible reasons have been theorized. Humidified air is heavier than drier air because it contains water droplets and may be more difficult for those with asthma to breathe. Areas with high humidity also have higher rates of mold and fungi. Dust mites tend to thrive in humid environments, which are another potential asthma trigger.

Moving to drier climates may not necessarily be the answer, as extremely dry areas may have increased smog levels. The dry air may also irritate sensitive upper air passages and make asthma worse. So what should asthmatics do to help control he humidity in their environment? Air conditioners will help dry the air. Dehumidifiers may also be helpful, although avoid those that create ozone as this will aggravate asthma. Make sure to empty the water trays on the refrigerator, dehumidifier, and air conditioner regularly to lower the humidity and decrease the buildup of mold. It might also be helpful to purchase a humidity gauge to monitor the levels in your home. Try to keep the levels close to 35 to 50 % humidity.


Although humidity is only one factor that may trigger asthma, it also may be able to be controlled to at least a certain extent. And put away the humidifier for your wheezing asthmatic child—now you know best.