Why Does Air Conditioning and Heating Make Dry Eyes Worse?

By Alison Daoud, Australian Optometrist and Dermii Co-founder

What's actually happening in climate-controlled air

Normal outdoor humidity sits somewhere between 30 and 60 percent depending on the day. Both air conditioning and heating systems typically bring indoor humidity down well below that, often into the 20 to 30 percent range, sometimes lower in a heavily heated room in winter. Dry air increases what's called evaporative loss from any exposed wet surface, including the surface of your eye.

Your tear film is a thin, layered film made mostly of water with an oil layer on top designed to slow that evaporation down. In dry air, evaporation speeds up. If the oil layer is already thin or patchy, there's less to slow it, and the water layer disappears faster than your eyes can replenish it.

Heating and air conditioning cause the same problem, just in different seasons

It's easy to think of dry eyes as a winter problem because heating is the obvious culprit in cold months. But summer air conditioning does the same thing to indoor humidity, sometimes more aggressively, because cooling systems actively strip moisture out of the air as part of how they work.

If your eyes feel worse at your desk in January and worse at your desk in July, that's not two separate problems. It's the same mechanism showing up under two different systems. This is worth knowing because it means the fix isn't seasonal either. A lid hygiene routine that works in winter works exactly the same way in summer.

Why blink rate makes it worse

Dry air alone would be a manageable problem if blink rate stayed normal, because a full, complete blink refreshes the tear film and releases oil with every pass. The trouble is that the rooms where climate control is strongest, offices, cars, planes, are also the rooms where people are usually sitting still, often looking at a screen.

So you get thinner air and fewer blinks at the same time, in the same room, for hours at a stretch. Each factor alone would cause some dryness. Together, they compound.

The spaces where this hits hardest

Some environments combine every risk factor at once. Open-plan offices with central air conditioning and everyone looking at screens are a common one. Cars with the heater or aircon running on a long drive are another, especially with eyes fixed on the road rather than blinking naturally. Aeroplane cabins take it further again, with humidity that can drop into the single digits alongside hours of screen use.

Bedrooms with a heater running overnight are an underrated one too. Many people wake up with eyes that feel worse than when they went to sleep, and an overnight heater drying out the room while the eyes are closed but the tear film is still working is often part of why.

What helps in the room itself

A few environmental changes take some pressure off. Running a humidifier in a heated bedroom or a heavily air-conditioned office genuinely helps if the humidity is very low. Positioning a desk away from a direct aircon vent makes a measurable difference, since direct airflow across the eyes accelerates evaporation further. Taking real breaks to blink fully and deliberately every hour, not just glancing away from the screen, helps counter the reduced blink rate.

None of these fix the underlying oil layer on their own, but they reduce how hard that layer has to work.

What actually addresses the underlying mechanism

Environmental fixes manage the trigger. They don't rebuild the oil layer that's supposed to be protecting your tear film in the first place. That comes from the glands along your lid margin functioning properly, which means keeping that margin clean and giving the glands regular warmth to help release the oil they produce.

The Dermii routine does this in ninety seconds, twice a day. The Lid Love wipes clean the lash line of the debris and build-up that dry air and reduced blinking make worse. The Miracle Mist, a hypochlorous acid spray, supports a clean lid environment between cleanses without rinsing. The Self-Warming Eye Mask, used every third evening, holds warmth at the lid margin for fifteen to twenty minutes to help soften and release oil that's built up in the glands.

The Lid Lover Starter Bundle covers all three steps of this routine.

When to see your optometrist

If dryness in air-conditioned or heated rooms is severe, doesn't ease with consistent daily lid hygiene after three to four weeks, or comes with vision changes, real pain rather than discomfort, or redness that won't settle, please see your eye care professional. Climate-related dryness is common, but it isn't the only possible explanation for persistent eye discomfort.

Frequently asked questions