Can air conditioning make you sick?
Short version: air conditioning itself doesn't cause colds or flu — viruses do — but a badly maintained or badly used system can genuinely cause dryness, irritation and, in a poorly kept unit, circulate mould and dust that trigger symptoms. Every real "AC sickness" complaint traces to one of three fixable things: dirty equipment, aggressive settings, or dry air. Meanwhile the health case for cooling is stronger than most people realise — heat killed around 3,000 people in Britain in 2022, and studies suggest air conditioning can prevent roughly three-quarters of heat-related deaths (figures on our statistics page). So the honest framing isn't "is AC bad for you" but "how do you get the protection without the irritation".
The complaints that are real — and their fixes
- Sore throat, dry eyes, dry skin. Real, and it's the dehumidification: cooling strips moisture, and hours in very dry, cool air dries out your airways — which can also make you slightly more susceptible to whatever virus you meet. Fixes: don't run colder than you need (24–25°C is comfort, 19°C is a throat-drier), take breaks from the conditioned room, stay hydrated, and don't point the airflow directly at your face or bed — swing/diffuse modes exist for this.
- Musty smell and allergy-type symptoms. Real, and it's the machine, not the concept: a damp coil, dirty filter or clogged condensate drain grows mould and bacteria, and the fan then distributes them. The fix is boring and total: clean filters every few weeks in season, run fan-only after cooling to dry the coil, annual service for split systems. A clean AC actually filters dust and pollen from room air — many hay fever sufferers find a well-maintained unit with windows shut is the best August they've had. Our troubleshooting and maintenance guide covers all of it.
- "I always get a summer cold at work but not at home." Plausibly real, but the culprit is shared indoor spaces and recirculated air in buildings with many people — i.e., proximity to other people's viruses — plus dryness lowering your defences. Domestic single-room systems don't recreate office conditions.
- Aches and stiffness from cold draughts. Real for some people — sitting in a direct cold stream tenses muscles. Same fix as dryness: sensible temperature, airflow directed away from people.
The worries that are mostly myth (for home systems)
- "Air conditioning spreads Legionnaires' disease." For UK domestic split and portable units: effectively a non-issue. Legionella needs warm stagnant water systems — the outbreaks you've read about involve large cooling towers and poorly maintained commercial water systems, not the sealed refrigerant circuit and condensate drain of a home split unit. Keep the drain clear (which you're doing anyway) and this is not a risk worth your worry.
- "AC recirculates the same stale air all day." Home split units cool and filter the room's own air — they neither import fresh air nor make air "stale"; CO₂ builds up in any closed room with people in it, AC or not. Crack a window periodically or air the room between sessions, exactly as you would anyway.
- "Sleeping with AC on is bad for you." The evidence points the other way: sleep quality degrades measurably above ~24°C, and cooling a bedroom to 20–24°C generally improves sleep. The genuine caveats are the ones above — not too cold, not blowing on you, clean filters — plus using sleep/timer modes so the room doesn't over-chill at 4am.
The health case for cooling, briefly
Heat is the actual danger in this story. Overheated homes disrupt sleep, strain the cardiovascular system, and in heatwaves kill — disproportionately the elderly, who are among the least likely to have cooling (the "cooling divide" data is on our statistics page). For vulnerable people, a cooled room during a heatwave isn't a comfort purchase; it's closer to a safety measure. If that's the situation you're buying for, size the room properly and consider a quiet split over a portable for a bedroom — the noise difference matters most for exactly the people who need the cooling most (comparison here).
The whole answer in one line: keep it clean, keep it at 24°C not 19°C, don't sit in the draught — and air conditioning is comfortably net-positive for your health, especially in the summers Britain now gets.
Quick answers
Can air conditioning give you a sore throat?
Indirectly, yes — very dry, cold air for long periods dries the throat and airways, and a dirty unit circulating mould or dust can irritate them further. Moderate temperature settings, airflow pointed away from you, hydration and clean filters resolve it for almost everyone.
Is air conditioning bad for asthma or hay fever?
A well-maintained unit is usually a benefit — it filters particles and lets you keep windows shut during high pollen counts, and dehumidified air discourages dust mites and mould. A neglected unit can do the opposite. The filter-cleaning habit is the difference between the two.
What's the healthiest temperature to set air conditioning to?
For comfort and airway-friendliness, 24–25°C with modest fan speed suits most people — cool enough to sleep and function, warm enough to avoid the dryness and draught complaints. It's also markedly cheaper to run than arctic settings (running costs here).