DRY WINTER MORNINGS AND SENSITIVE SINUSES

My nose bleeds every winter morning and I never worked out why

Why do I get nosebleeds in winter?

Because heated indoor air in cold weather is extremely dry. Cold outdoor air carries almost no water, and warming it indoors adds none — so the relative humidity collapses, the mucous membranes lining the nose dry out and crack, and the blood vessels just under them are easily disturbed.

It happens in the same weeks every year. A cold snap arrives, and two or three mornings later you are standing at the basin at seven in the morning holding a tissue.

Then it stops in spring, as reliably as it started.

The mechanism

The lining of the nose is a mucous membrane, kept moist to trap dust and pathogens on the way in. Immediately beneath it, particularly at the front of the septum, sits an unusually dense network of small blood vessels.

Dry air draws water out of that membrane. It thins, cracks, and the vessels underneath become easy to disturb — by a sneeze, by blowing, or by nothing much at all.

You are also breathing that air for seven or eight hours overnight without drinking, which is why the pattern is a morning one.

Why winter air is so dry indoors

This is the part that is genuinely counterintuitive, and the forecast actively misleads.

Cold outdoor air carries very little water however high its percentage reads. Bring it inside and warm it — no water is added, but the amount the air could hold rises steeply, so the relative humidity collapses.

The same outdoor air, brought in and warmed to 21°C.
Outside	Water carried	Indoors reads
10°C at 70%	6.6 g/m³	36%
0°C at 80%	3.9 g/m³	21%
−10°C at 90%	2.1 g/m³	12%

A cold snap at −10°C produces indoor air drier than most deserts — and the forecast that day says 90% humidity.

That contradiction is why the connection is so rarely made, and it is exactly what the absolute figure exists to resolve. The heating is not drying your air; the air was always that dry, and warming it revealed the fact.

What helps

A humidifier in the bedroom. The direct fix, and it targets the hours that matter. Keep it clean.
Aim for 30–50%. The same range recommended for comfort generally.
Do not over-ventilate in a hard freeze. Ventilation exchanges your indoor air for extremely dry outdoor air. Enough for air quality, not more.
A saline spray or ointment keeps the membrane itself moist, which is treating the symptom rather than the cause — entirely reasonable when the cause is the weather outside.
Drying laundry indoors, unusually, is helpful in a dry cold spell. It adds water to air that has almost none.

The rest of the pattern

Winter nosebleeds rarely arrive alone. The same threshold produces static shocks from every doorknob, chapped lips, gritty eyes and a sore throat on waking — the whole set, from one variable.

If several of those started in the same week, that is the diagnosis.

Not medical advice

This describes a mechanism, and it is a real and well-recognised one. But nosebleeds have plenty of other causes, and frequent, heavy or hard-to-stop ones — particularly with bruising elsewhere or after a medication change — are worth taking to a doctor rather than attributing to the weather.

Common questions

Does dry air cause nosebleeds?

It is a well-recognised contributor. Dry air draws moisture from the mucous membranes lining the nose, which can crack and expose the dense network of small blood vessels just beneath. That is why winter nosebleeds are so much more common than summer ones.

What humidity prevents nosebleeds?

Keeping indoor relative humidity in the 30–50% range removes the dryness contribution. That is the same band recommended for comfort generally, so there is no trade-off in aiming for it.

Why are they worse in the morning?

Because you have spent seven or eight hours breathing dry air without drinking, so the membranes are at their driest. Sleeping with the mouth open, or with heating running all night, makes it more pronounced.

Will a humidifier help?

It addresses the cause, yes. A bedroom humidifier is the common recommendation for exactly this pattern. Keep it clean — a dirty reservoir aerosolises whatever is growing in it.

When should I see a doctor about nosebleeds?

If they are frequent, heavy, hard to stop, come with bruising elsewhere, or start after a change in medication. Dry air is a common contributor and it is not the only possible cause, so persistent nosebleeds are worth having looked at properly.

Sources

ASHRAE Standard 55 — Thermal Environmental Conditions for Human Occupancy — Source of the 30–50% comfort range
WHO Guidelines for Indoor Air Quality — Dampness and Mould

Published 12 August 2026