Humidifier or dehumidifier? - Asthma UK communi...

Asthma UK community forum
15,703 members20,424 posts

Humidifier or dehumidifier?


Hi guys- quick question regarding my sons asthma. He has constant recurrent chest infections and asthma flare ups - especially during the winter months. He usually has the salbutamol inhaler for general use and prednislone when his chest is worse. I just can't figure out what triggers it off with him as one day he's fine and the next he wakes with a cough and is very phlegmy. His asthma nurse recommended a humidifier - but as we have a slight mould growth issue upstairs I'm wondering if a dehumidifier may be better? We live in rented property and don't have double glazing and our landlord refuses to pay to have it done so our windows become heavily condensates during the winter months. It's such a difficult situation as I know there needs to be ventilation but opening windows during the winter months is not something I want to do. Does anyone have any tips for how i could help his asthma? It's so frustrating for him to have a bad chest, it goes and then a week later it returns.

9 Replies

Hi there sounds like you are in a tricky situation. There are a few things I can suggest.

Even though you don't want to open the windows upstairs and down, it's a really good idea to get a free flow of fresh air running through the house every day. (Unless you live on a very busy street with lots of fumes or there is a very high pollen count.) Even if it seems awful to let all the heat out, opening the windows helps to clear fungal spores and mould spores from the house even if you only leave them open for 30 minutes.

A dehumidifier is a good idea if your house is at all damp as it will help dry up the the mould. If you can see mould growing anywhere as a stop gap thing, paint it with bleach and let it dry, (or you can buy specialises products) when your child is out.

You can also buy a great product from lakeland that helps get rid of condensation, they are crystals that absorb water.

However, you don't say how old your son is, if he is very young then a humidifier in his bedroom, when he is phlegmy might be a very good idea.

You say you go straight from Ventolin to him taking courses of prednisolone, which seems a bit drastic. May be it would be good to talk to the doctor about getting him an inhaled steroid with a spacer that he can use every day. This worked wonders for my daughter when she was only 3. I also found that paediatric singulair was really helpful for her when she was a little older.

If you continue to have problems you might ask your G/P for a referral for allergy testing to see what he is actually allergic to, i.e. fungal spores, dust mites, pollens, animals. Then it is easier to know what to avoid.

Other quick tips, wash all his bedding on a high temperature, and wash duvets and pillow regularly too, with non bio liquid. Regularly put teddies in plastic bags then put them in the freezer for an hour. Hoover his mattress at least once a week more if you have time.

Ideally have a hard floor in the bedroom, but if not, use a vacuum with a hepa filter regularly. (Carpets and Underlay can be a real problem particularly if there is mould as it can grow underneath the surface). Think about getting it professionally cleaned if you can afford to. Or you could rent a carpet washer. Take out curtains and use blinds instead.

I wish you the very best of luck. I know it is not easy being in rented accommodation and it can be very worrying and frightening to have a child with asthma. I have asthma and my daughter who is now grown up has asthma, we had some scary moments with her when she was little.

R x

in reply to risabel59

Thanks so much for replying - yes it's a pain in the winter as you want to keep warm but have to ventilate upstairs. The bathroom is the worst for mould and his room is right next to it so I'm thinking a dehumidifier all round may help. My sons 8 also btw.

I'm definitely going to ask for allergy testing. It's a complete nightmare at our local surgery even getting an appointment but I want to try and do whatever I can to at least a alleviate his symptoms as it's just a constant weekly struggle. He uses his blue inhaler daily but they always seem to give him the prednislone whenever I bring him in. He's just finished a fortnight dose of amoxicillin for his chest too. He misses a lot of school due to this too which is a nightmare for me being pestered by them but what do you do when you have a poorly child.

I'm going to bleach his walls later and get another crystal absorber for his window. A family member has a dehumidifier so I'm going to ask to borrow if to see just how much moisture it sucks up - we have no problems with mould downstairs it's just up. Upstairs is carpeted too unfortunately but I do give it thorough hoovering and I have a carpet washer so I'll have to get that out and give it a once over in his room.

Thanks so much for all your advice though it's been helpful :)

in reply to Sonsmum

You might also like to try calling the Asthma UK helpline. The Asthma UK nurse will be helpful in telling you how to approach your G/P. If your son is using that much ventolin, he probably be ought to be using a preventer (steroid) inhaler.

Your son should have a written asthma plan. (that is part of NHS guidelines). I think you can print out one from the main asthma uk site, which you can then take to your G/P's to fill in with them. But honestly your surgery should have the forms. Also ask for a prescription for a peak flow meter, so you can monitor when things are getting worse. Your G/P or asthma nurse should show you how to use it. (It really helps to have a record of how things have been going when being pushed from pillar to post in a G/P practice)

Uncontrolled asthma in children can affect their growth and other things. Low dose steroid inhalers have a pretty good record. My Daughter is 5ft 9ins now and has used them since she was 3.

Just for reference, My consultant considers my asthma to be uncontrolled if I am using my ventolin more than 3 times in a week, (outside of exercise). And then I have to change up my medication.

Good Luck with your Surgery, I've had some nightmare doctors in my time. Asthma UK has really helped me.


Oh and by the way here is the link to the Asthma plan, You can print and take to your GP's next time.

Hi Sonsmum, if you think the mould is contributing to your son's asthma., which it probably is, then it would be possible to have your council send someone from their environmental health dept to assess the quality/safety of your housing. They will be able to help the landlord to comply with regulatioins.

If it's black-spot mould then that is usually associated with condensation in poorly ventilated rooms, it is a health hazard. I don't know much about other moulds but I imagine they're even worse.

Mould spores bloom and spread like nothing else and are invisible in the main.

Fungicides as well as bleach are available.

I have a dehumidifier that I bought recently - a Challenge model from Argos, it was reduced to a hundred quid, it's compact, very noisy and very heavy and works brilliantly but I use it in my workshop! It doesn't measure room humidity - I have a separate hygrometer for that so I know how long to dehumidify for.

Hygrometers are often incorporated into digital weatherstations and are cheap, I got mine years ago from Maplin I think. it's called 'InnoValley Weather Station'

It may well be worth buying a decent-sized HEPA air purifier- I've owned several over the years and swear by them. They will catch a lot of particles including mould. Avoid the ones with ionizers and ignore the gimmicky miniature table-top ones. There are many posts (incl. mine) about air purifiers on this website.

Ultimately it's best to live in an environment that is optimum for your son's health but there are many interim tweaks that can help.

Lino seems to be the most hypoallergenic flooring.

Also, be aware that an upheaval such as decorating or new flooring will increase the concentrations of airborne hazards for some time (days/weeks) until it settles down. And that after a big exposure/attack, an asthmatic will be more sensitive than usual to irritants until the inflammation repairs.

I hope this helps, the other replies give excellent advice already too, cheers. Ollie


Not asthma related but a cheap way to reduce condensation is with cat litter and old socks. Fill the sock with cat litter tie a knot on it and lay around when soggy throw away.

I live in a fully insulated bungalow and had trouble with condensation. We bought an e.bac dehumidifier and have it in the hall magic no more black mould windows do get misty but easy to dry them. We bought one more powerful than needed just to make sure. We rang the people at e.bac very helpful, pointed out that someone was selling their product cheaper than them and they price matched good luck :-)

Mould spores are probably the main danger to anyone’s health. Humidity or Moisture in the air or RH or Relative Humidity explained. First and important concept is that warm air holds more water. When that warm air meets a cold surface the water drops out of the air on to that surface, such as a single glazed window.

When it drops out onto a poorly insulated wall is where the mould trouble starts. Mould loves moisture. Walls absorb moisture and remain damp throughout the day.

These damp spots where mould grows will often coincide with some building defect like a cavity wall bridged or an old ceiling with a perfect timber bridging above the ceiling such that the cold is easily conducted inside the home such that in some case the mould follows these hidden ceiling timbers in a geometric pattern of growth.

Now how to stop it in a rental property. You could Phone your local council Environmental health and ask them to come and look. Do not be surprised if they and the landlord say it is your fault, open a window. Be ready for this and explain you have and point out the single glazing and the uninsulated walls and the standard bleach solution cleaning to kill and contain the mould spores.

Now the good bits, Number one, the council can force the landlord to improve your property. This is by far the best option stick out for this. Failing that, Number two, attack the mould at it basic level. Ie mould can only grow when the RH is above 70%. Here is a good leaflet from Wavery Council that will explain this:-

You can buy a cheap RH% meter from Ebay for a few pounds. Like this:-

I would buy a few of these and place them around the house and keep readings meticulously over a couple of weeks prior to calling in environmental health. This will show them that you understand the dangers of humidly and have taken serious steps to minimise operating your home in way that will add to the already present problem.

Remember if the humidly is below 65% then the mould just cannot function, you have shut it down, stopped it in its tracks. This should be backed up with continued scrubbing with a good fungicide (while son is out preferably) over the mould spots after or if the council will not either get the landlord to fix the problem or move you into better accommodation.

Google will give you the ideal RH% for an asthmatic sufferer. This website:-

tells me that the ideal RH% is between 45% and 55%. As you see this range is below that at which mould can survive so ideally. Dehumidify to this level. Remember always over estimate your need in the volume you want to dehumidify. It is easier to turn things down that to get more capacity at a later date.

If after all this you are stuck there or need a quick ongoing fix then consider a ‘heat recovery fan’ if not for the whole house then just for your sons bedroom.

A heat recovery fan will suck the warm damp air out of the room then pass it over a ‘heat exchanger within the unit where cold dry incoming air will ‘recover’ some of your expensive heat using it to warm up the incoming dry air.

These units will need two connections to the outside air. In a rental property is you are not allowed to make two holes in the wall then consider removing two panes of glass from ideally two widely separated windows. One for intake and one for exhaust air.

The actual heat exchanging is taken care of in the unit by vanes or close coupling the outgoing and incoming air while not actually having them in physical contact. Some of these units will recover a high percentage of your heat.

Here is the type of heat recovery unit:-

These are made for above ceiling mounting although other types are available this will give you an idea of the concept.

Here is one for a single 10 cm diameter wall mounting:-

Don’t to choose a unit that can have the incoming air filtered as you do not want to suck in contaminated air!

It is a case of googling and taking advice to arrive at a solution suitable for your home.

Look at the watts power each solution uses as well to get an idea of running costs. The last example above claim 78% heat recovery using only 2watts. This will go up however if you introduce filters so making the fan work harder.

If you go for the higher running cost of an air conditioner/dehumidifier then the type using a supply and exhaust hose is best. Remember to check the manual before buying to see if it is possible to filter the air sufficiently as you are recirculating the house air, spores and all. So filtering is a must with these units. The hoses merely dump the condenser air outside.

All of these solutions will produce ‘condensate water’ which should be either plumber to outside where it can drip away or in some wheel around packaged air conditioner/humidifiers this is collected in a tank which has to be emptied about once a day. Remember to treat this tank with a suitable fungicide periodically as recommended, hidden water is always a place for things to grow.

Lastly good double glazing and insulated walls with well-maintained structure like walls and guttering are by far the cheapest way for an occupier to g. Everything you do without the basics being right in the first place are going to cost in initial outlay and running cost. I would put together a good case for Environmental Health to rehouse you as being the best option. That means Photographs, temperatures and RH% readings all taken and tabulated, then the Environmental Health visit.

Too low or too high humidity could trigger asthma symptoms. As you know, high humidity is reduced by a dehumidifier whereas a humidifier increases the humidity level of a room. Since your son suffers most during the winter, I’d personally recommend that you get a humidifier because it will remove the dry air in the room (dry air is one of the common asthma triggers). A dehumidifier will be effective in stopping mold growth, but a humidifier will be more effective in improving your son's condition.

You may also like...