Why your skin got worse when the heating went on

Cold outdoor air holds very little water. Bring it indoors and heat it to twenty-one degrees and its relative humidity collapses. A heated British living room in January often sits somewhere in the twenties or low thirties. That’s drier than a good deal of the Mediterranean in summer.

Dry air is thirsty air. Water leaves your skin continuously by evaporation, and the drier the air above it, the faster that happens. Your skin isn’t producing less moisture in winter. It’s losing more, all day, in every heated room you sit in.

The outermost layer of skin works like a wall: cells as the bricks, a mixture of lipids as the mortar. That mortar is what holds water in. When water leaves faster than it can be replaced, the mortar stiffens and cracks at a microscopic level. Once that happens, two things follow.

Water leaves faster still, so it accelerates. And things that used to sit harmlessly on the surface now get through: fragrance, preservatives, the acid in your serum, the alcohol in your toner. This is why the sequence is so consistent. Tightness first, then flaking, then products that used to be fine start to sting.

It’s also why people conclude their skin has ‘become sensitive’. Usually it hasn’t. It has become sensitised, which is a different thing and a reversible one.

This is the part that stops people connecting the two. The heating goes on in the third week of October and nothing happens. Skin is a slow organ. The surface layer you’re looking at today was formed several weeks ago. The barrier has reserves it can run down before anything is visible.

So the symptoms arrive in the middle of November. By then the boiler is part of the furniture, and the obvious suspect is the new serum you started, or the weather, or your age. I’ve had this conversation every winter for twenty years, and the answer is almost always the same. So I’m writing it down in January, rather than in October when nobody would read it.

The same lag works in your favour going the other way. If you change the routine now, expect two to three weeks before the tightness properly settles. Judging it after four days and adding something else is how people end up with nine products.

It isn’t only the dryness. Going from a cold street into a heated shop, or from a heated office out into the wind, makes the facial blood vessels dilate and constrict repeatedly. For most people that’s just a flush that fades. For anyone prone to redness it’s one of the most reliable triggers there is. That’s why rosacea so often announces itself in the same fortnight.

The hot shower makes it worse, and I know that’s an unwelcome sentence in January.

Cleanser first. Anything that foams enthusiastically or leaves the face feeling squeaky comes out. A cream or milk cleanser, lukewarm water, and once a day at night rather than twice.

Then the mortar. Something with ceramides or a good occlusive over the top of whatever hydrating serum you use: water-binding ingredients underneath, lipids on top. In the other order it evaporates, taking your serum with it.

Then the air. A humidifier in the bedroom, set somewhere around forty to fifty per cent, is the single most effective change on this list. It’s also the one people are most reluctant to make. Eight hours a night of air that isn’t pulling water out of you is worth more than any product I could sell you.

And sunscreen still, every morning. Winter UV is lower rather than absent. It’s easy to let it go when the sky is grey, and that’s usually all that has happened.

• Acids, for two to four weeks. Not forever. The barrier can’t rebuild while it’s being dissolved every third night.
• Retinoid frequency, halved, until the tightness settles.
• Any physical exfoliation at all. Flaking skin is a symptom, and scrubbing it off treats the evidence rather than the cause.
• Long hot showers on the face. Wash your face at the basin, not under the water.

If the tightness comes with a rash, itching that keeps you awake, weeping, or patches with a clear edge to them, that’s worth a GP appointment rather than a facial. Eczema, seborrhoeic dermatitis and perioral dermatitis all worsen in winter and all need something other than a better moisturiser.

And if this happens every single year, it’s worth planning for October rather than reacting in December. Most people’s winter skin is manageable if the routine changes before the symptoms arrive.