When little ones are struggling with a cold or flu, it can be difficult to help them get a good night’s rest.

Parents are marketed a range of “solutions”, including using a humidifier or vaporiser, which it is often claimed can help alleviate stuffy noses, reduce coughs, and help prevent the spread of viruses.

But is there any evidence they work? And are they safe for babies and children?

How do humidifiers and vaporisers work?

A humidifier is a device that adds moisture to the air via a fine mist.

There are different types of humidifiers, including cool mist, warm mist, and ultrasonic.

Vaporisers basically do the same thing as warm mist humidifiers, but are designed to heat and evaporate substances, like essential oils or menthol products, explains Brian Oliver, a respiratory researcher at the University of Technology Sydney.

He says a comfortable humidity level in the home is between 40 and 60 per cent.

High and low humidity levels can have an impact on respiratory health, which we will dive into shortly.

To know what the humidity is in your home, you can use a hygrometer, a relatively inexpensive gadget used to measure the moisture content in the air.

What the science says about humidifiers and health

While humidifiers and vaporises can help add humidity to dry air, health claims that they help with cold and flu symptoms are unproven, says Professor Oliver.

“These claims are made by people with a financial interest in selling humidifiers … they’re not really made from scientific investigation,” he says.

He says there is also “no clinical evidence that humidifiers help babies to sleep better”.

Pamela Douglas, a Brisbane-based GP and researcher into post-birth care and unsettled babies, also says there is no evidence to suggest these devices improve sleep in babies and toddlers.

“Not even a little one who has a cold or upper-respiratory tract infection,” says Dr Douglas, who is also the medical director of The NDC (Neuroprotective Developmental Care) Institute.

Dr Douglas says it does, however, raise the issue of air-conditioner use.

She says humidifiers are often used by people to compensate for the use of air conditioners, which dry out the air.

“Throughout my professional life, if a little one has been prone to recurrent respiratory tract infections, I’ll suggest the family reconsider how often they have air conditioning or fans on during the night.”

It’s worth noting for infant sleep safety, Red Nose Australia does not recommend a specific room temperature for baby’s sleep.

“And given we are looking at low carbon emissions futures, I’m very supportive of minimising our aircon use — reserving it for those days when we really need [it]. And otherwise allowing babies and toddlers to acclimatise with natural ventilation at night and during the day,” Dr Douglas says.

This is “of course climate dependent”, she adds, but says the more natural ventilation we can have, the better.

For example, a recent study from China showed bedrooms with low ventilation were associated with an increased risk of pneumonia in children.

Asthma Australia’s director of health knowledge and translation Anthony Flynn says in some parts of Australia, it may be that a focus on reducing humidity in a room is necessary.

“To reduce humidity in your home, purchase a dehumidifier or use the dry option on your reverse-cycle air conditioner or heat pump.

“Use exhaust fans in the bathroom, laundry and kitchen. Close windows and doors when humidity outside is high. During periods of drier weather, open windows to help keep moisture away.”

Is using humidifiers safe?

Professor Oliver says while many manufacturers state their products are safe, “the use of humidifiers might pose a risk”.

For example, many devices don’t let you control the levels of humidity being added.

“You don’t want something chugging away in the corner producer lots of water uncontrollably,” Professor Oliver says.

When a room becomes too humid, he says that creates the risk of mould, mildew, and dampness.

Mr Flynn says dust mites also thrive in humid environments.

“We don’t recommend humidifiers as the extra moisture in the air can encourage mould growth and also create great conditions for dust mites, which are both common asthma triggers,” Mr Flynn says.

“Some people find that humidifiers help if cold dry air is a trigger, but they should be used with caution and ventilation is key.”

Dr Douglas says parents who want to use these devises should opt for cool-mist only, as those that boil water or emit steam are a burns risk to infants and children.

Professor Oliver warns that aerosolising tap water also means microbes can enter lungs and cause infection, so using distilled or boiling water is recommended.

Devices also need to be cleaned regularly to prevent the growth of mould and bacteria.

“In all cases it’s really important that a parent speak to their health care provider to seek medical advice around the use of a humidifier,” Professor Oliver says.

Wakeful nights during illness are normal

It’s understandable parents want to do what they can to help their babies and toddlers to sleep better, says Dr Douglas, but “very disrupted nights” are to be expected when children are unwell.

“Parents need to be reassured, really miserable and disrupted nights can be expected when a little one has an upper respiratory infection.”

She says more generally, a focus on “controlling environments” for baby sleep isn’t always helpful.

“The idea that you need to maintain a certain humidity or air temperature to help babies sleep better is not evidence based, and shifts the focus away from things we can do to avoid excessive night waking and make sleep easy and manageable for a family.”

This is general information only. For detailed personal advice, you should see a qualified medical practitioner who knows your medical history.