Dry or dehydrated? They are not the same problem

Dry skin doesn’t produce much sebum. It’s a type. You’ve had it since your twenties, it runs in your family, it flakes, and it feels tight all over rather than in patches. Always worse in winter.

Dehydrated skin doesn’t hold enough water. It’s a condition and it’s temporary, and it usually comes from something ordinary: over-cleansing, a new acid, a flight, a fortnight of wine and late nights, air conditioning, a heated house.

You can be oily and dehydrated at once. That combination is really common, and almost nobody recognises it in themselves, because the shine argues against the diagnosis.

Wash your face and put nothing on it. Wait half an hour and then look properly, in daylight, near a window.

If the whole face feels tight and slightly rough, if there’s fine flaking around the nose and brows, and if it looks matte everywhere including the forehead by mid-afternoon, that’s dry. It has probably been that way for years.

If it feels tight but you can still see shine on the nose and forehead by afternoon, if fine lines look more visible than they did last month, and if the skin looks a bit dull and crêped when you pinch the cheek gently, that’s dehydration. The giveaway is that it changed recently. Skin type doesn’t change in a fortnight. Skin condition does.

Two other tells worth knowing. Dehydrated skin often stings slightly when you apply something that used to be fine. That’s the barrier letting things through it should be keeping out. And make-up behaves differently. On dehydrated skin, foundation clings to fine lines and separates across the cheeks by mid-afternoon. On genuinely dry skin it tends to look powdery and flat from the moment it goes on.

Dry is a type. Dehydrated is a condition. If it got worse this month, it’s a condition, and conditions can be reversed.

Someone with oily skin treats the oil. Foaming cleanser twice a day, an acid toner, a clay mask at the weekend, blotting papers. All of that strips the lipids that were holding water in. So the skin loses water, feels tight, and responds to feeling tight by producing more oil.

The shine goes up, so the routine escalates. I see this most in people in their thirties and forties who are still using the routine that worked at nineteen. It’s one of the quickest things to put right, usually within three or four weeks of doing considerably less.

Lipids, and more of them than you think. Ceramides, cholesterol, fatty acids, squalane, a facial oil at night if you like the feel of one. A cream cleanser rather than a gel. Nothing that foams.

Dry skin is a type, so this is maintenance rather than a course of treatment. It’s supported well and continuously, and it doesn’t go away. That isn’t a disappointing sentence, it’s just an accurate one.

Water-binding ingredients: glycerin, hyaluronic acid, polyglutamic acid, urea at low percentages. Applied to damp skin, then sealed with something above them. And, more importantly, the removal of whatever caused it.

That last part is the bit people skip. Layering a hydrating serum over a routine that’s still stripping the skin twice a day is pouring water into a bucket with a hole in it. Take the acid out for a fortnight, change the cleanser, and the serum will suddenly seem to be working much better.

If you’re oily and dehydrated, the layer on top doesn’t have to be a heavy cream. A light lotion with some lipid content is plenty, and it’s far more likely to be used every night than something that feels like a mask. The seal matters more than its weight.

Damp skin, then the water-binding layer, then the lipid layer on top. Applied to bone-dry skin, a hyaluronic serum has very little water available to bind and, in dry air, can end up pulling it from the skin instead. Applied under nothing at all, whatever it drew in evaporates within the hour.

This is the single most common thing I change in a routine, and it costs nothing to do.

Being properly hydrated is good for you, and I’m not going to argue against it. But if you’re already drinking a normal amount, another litre a day won’t resolve dehydrated skin. It’s happening at the surface. Water is leaving through the barrier faster than it’s arriving.

Get the barrier working and the water stays where you put it. That’s the whole of it.