Dry eyes from a space heater

A space heater can dry your eyes because it warms air without adding moisture, and many push that warm, drier air straight at you. When the stream reaches face level, it speeds evaporation from the tear film. Aiming the heater at your feet or legs, moving it a few feet away, adding humidity to the room and keeping your eye drops well clear of it all help.

Dry eyes due to a heater: what’s happening

Warming air lowers its relative humidity unless water is added at the same time. A space heater does the warming without the water, so the air around it is drier than the rest of the room. Fan-forced heaters then blow that air in a stream, which works on your eyes the way a breeze does outdoors: it moves dry air across the eye’s surface between every blink.

The tear film is the part that loses out. It’s made of a mucus layer, a watery layer and a thin oil layer on top that slows evaporation. A steady stream of warm, dry air thins it faster than usual, and the eye can start to feel gritty, tired or tight within an hour or two.

Placement: where the heater goes matters most

• Aim it low. Pointing the heater at your feet and legs warms you without sending air past your face.
• Put some distance in. A heater a few feet away, angled across the room, warms the space with far less airflow on your eyes than one right beside your chair.
• Use oscillation thoughtfully. A heater that sweeps back and forth at head height sends a pulse of air at your face on every pass.
• Check the manufacturer’s instructions for clearances. Distance from furniture, bedding and curtains is set by the maker for safety, and that comes before comfort.

Airflow at face level

A simple test: sit where you normally sit and hold the back of your hand in front of your eyes. If you can feel moving air there, so can your eyes. Lower the heater, turn it, or change the fan setting until the air at face height is still. A radiant or oil-filled heater that warms without a fan tends to move less air, though it still dries the room over time.

Under-desk heaters and home offices

Under-desk heaters are popular in cold home offices, and they’re usually low enough to keep air off the face. The trouble starts when the heater sits on the desk or a shelf and blows at you while you’re at a screen. Screen work already slows blinking, so dry air from the side plus fewer blinks hits the eye twice. Keep the heater at floor level and look away from the screen every so often; screens and your tear film has more on the blinking side.

Running a space heater in the bedroom

Bedrooms are where a heater runs longest with the door closed, so the air gets driest there. If you wake up with eyes that feel dry, look at where the heater points relative to the pillow. Aim it toward the foot of the bed or across the room, not at your head.

• Follow the maker’s instructions about running the heater while you sleep, timers and auto shut-off.
• A humidifier in the same room adds back what the heater takes away. Does a humidifier help dry eyes? covers the humidity range EPA recommends.
• A small hygrometer on the nightstand shows whether the room is getting too dry.
• A heater on a timer that stops before morning lets the air recover a bit before you wake.

Keep the bottle away from the heater

Eye drops have a storage range printed on the label. Quell’s reads: Store between 15° to 30°C (59° to 86°F). A bottle on the desk next to the heater, on the floor in its path or on top of it can warm far past the top of that range. Keep it in a drawer or on a shelf on the other side of the room, out of the heater’s airflow and out of reach of children. The storage line sits under Other information on the Drug Facts page.

If a bottle has been sitting near the heat, look at it before using it. The eye drops have a naturally milky-brown appearance. This is normal and does not indicate a problem with the product. The label’s Do not use line is clear: If this product changes color.

Using drops when the heater’s on

The label’s directions don’t change in winter: Apply 1 drop 3 times per day in each eye. On heater days, saving one drop for after you’ve been sitting near it for a while, rather than using all three early in the day, matches the drop to the drier air. Quell is designed to reinforce the tear film’s oil layer to help reduce moisture loss, the layer that slows evaporation in warm, dry air. Keep the tip clean: Do not touch tip of bottle to any surface to avoid contamination.

If your eyes stay uncomfortable even with the heater moved and the room more humid, something else may be going on. The label sets the line: Stop use and ask a doctor if you feel eye pain or changes in your vision, if irritation or redness continues, or if the condition worsens or persists for 72 hours.