One reason why your asthma may be worse in winter, and what to do

Chances are, if you live in one of the southern states of Australia, you maybe only think about humidity a couple of times a year.

That’s partially because we tend of only think about humidity in connection to long, hot, sticky days in summer, or how we console ourselves with not being able to afford a trip to a tropical island.

But, it’s probably something we should also be thinking about when the weather gets colder.

When it comes to humidity, you can have too much of a good thing.Credit:Tanya Lake

According to Dr Yuming Guo, head of the Climate, Air Quality Research Unit at Monash University, while low outdoor humidity in summer increases risk of death, high indoor humidity in winter should be more concerning in Australia.

“Because there’s a low temperature, it increases the relative humidity in the room,” he says. “And the relative humidity is related to mould, and that increases the risk to human health.”

Put simply, relative humidity measures the amount of water air can hold at that temperature. The higher the temperature, the more water air can hold. The lower the temperature, the less water. That’s why you get condensation on your windows and other cold surfaces in winter.

In fact, it’s not uncommon for newer dwellings, like well sealed apartments and suburban houses to experience 80 per cent or greater humidity in winter, especially given how pathetic a lot of bathroom extractor fans can be. Add in some wet laundry and boil some water on the stove, and you essentially have party conditions for mould and dust mites.

Dr Gao’s research shows that the safe range for humidity is 30 to 50 per cent.

But, according to the Australian Building Codes Board’s handbook on condensation in buildings, a family of four generates around seven to 22 kilograms of water vapour a day. With a family insisting on doing all of that breathing, cooking and bathing, even on a 20 degree day in a well-ventilated house, that can push the humidity to 50 per cent.

At 50 per cent humidity the dust mites proliferate. If the indoor temperature is 14 degrees, and those people are still going about their day normally, that brings the humidity to 70 per cent, which is when mould starts to germinate.

It’s not uncommon for newer dwellings, like well-sealed apartments and suburban houses to experience 80 per cent or greater humidity in winter.

That’s a problem not only for people who like their soft furnishings to be uncontaminated, but also for those with asthma.

Michele Goldman, CEO of Asthma Australia, lists the common triggers of asthma as “environmental exposures like smoke, either from bushfires, or wood heaters, or cigarettes, or dust, pollen, and mould”.

Although humidity doesn’t make that list of the top four most common triggers, it does worsen two of them, and many asthma sufferers have noticed their asthma worsening when the air feels “thicker”.

The good news is that there are plenty of ways to combat humidity and its associated problems.

Dr Guo’s tips are more technology based. “People should use the air conditioning, or the heating,” he says. “And maybe use a dehumidifier to reduce humidity in the house.”

Heating the air to reduce the humidity makes a lot of sense, though it’s difficult to manage on extra cold surfaces windows without raising electricity bills to unmanageable levels.

And, if you’re relying on an air conditioner, he says that can cause other problems.

“Think about ways to make the indoor air quality good, because when you use the air conditioner in the house, that can sometimes bring down the air quality, and that can also increase the risk to health.”

Ms Goldman’s tips are more centred around managing your own lungs.

“We're really cautious about encouraging people to purchase different kinds of products to help reduce exposure to triggers,” she says. “We know the burden of the cost of the medications is already quite significant among the large number of Australians who don't have health concession cards.

"Our advice would be that you use your medication and take it regularly, that's going to be a much better line of defence than out laying money on expensive products. Having said that, everybody's asthma is individual. And if people wish to try a dehumidifier, and they feel like it makes a difference to them, then by all means that's a complimentary strategy. But it shouldn't be in place of taking medication.”

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