Put lip balm on before the dentist

An hour in a dental chair does something to your mouth that goes unmentioned beforehand. It is held open and stretched, minute after minute, by somebody concentrating hard on a tooth. If your lips were at all dry when you arrived, they split — usually at the corners, usually on the way home.

Put a decent layer of something greasy on them in the waiting room. Say at the chair that you have. A number of practices already keep petroleum jelly by the light for exactly this, so it is a normal thing to raise rather than an odd one.

Lips have almost no oil of their own, so nothing you put on them moisturises them — the job is sealing water in, and plain petroleum jelly does that better than most things sold for it.

Sealing is a different job from moisturising

Most skin makes its own oil. Lips barely do. That single fact explains why they dry out faster than the rest of your face in the same weather, and it explains why the advice that works is not the advice that sounds sophisticated.

An occlusive is a physical film. It does not add moisture to anything; it stops what is already there from evaporating. That is why petroleum jelly — cheap, unscented, unglamorous — outperforms a great many expensive sticks, and why it works best applied to lips that are already slightly damp rather than to lips that have been dry all day.

It follows that drinking water is not the fix on its own, although this gets argued about. Being properly hydrated matters to your skin generally, and several people said it was the only thing that had ever worked for them. But water arriving from the inside does not stop evaporation from the outside, and if your lips are cracking in a cold wind, no amount of it will hold them.

Cold dry air is the other half. A humidifier in the bedroom helps if your nose is dry too, and a scarf pulled up over your mouth outdoors is doing the same job as the balm.

The one that reverses the usual advice

There is a widely repeated idea that lip balm is habit-forming — that your lips get used to it, stop looking after themselves, and need more and more. People describe the cycle accurately: apply, feel better, feel worse an hour later, apply again.

The cycle is real. The explanation is wrong, and the wrong explanation leads to the wrong action.

Lips do not have enough oil production to become lazy about. What is happening in most of those cases is irritation from what is in the stick. Menthol, camphor, phenol, salicylic acid and strong fragrances turn up in a lot of lip products, and they are there because the cooling tingle feels like evidence that something is working. For a fair number of people they are the cause of the dryness the balm was bought for.

So the instruction that follows is the opposite of the folk version. Do not stop using balm and tough it out on a cracked lip. Change to a boring one — nothing that tingles, nothing that smells of anything — and see what happens over a week.

Stop making it worse

Two habits undo everything else, and both are automatic.

Licking. Saliva evaporates fast and takes the lips’ own thin oil layer with it, so a dry lip you lick is drier a minute later, which is why you lick it again. This is the actual dependence loop in this subject. A layer of something greasy helps partly by sealing and partly by tasting of nothing, which is a reminder every time your tongue arrives.

Biting and picking at the loose skin. It bleeds, it scabs, the scab tightens and cracks, and you are further back than you started.

On exfoliating: people do recommend gently brushing the dead skin off with a soft toothbrush, and it does make lips smoother. The more cautious half of the argument has the better case — lip skin is very thin, and this is easy to overdo. Once a week at the outside, never on lips that are already broken, and never as a substitute for the sealing, which is the part doing the work.

When it is not just chapped lips

Two signposts, because they are things balm cannot fix and people spend months working through balms before finding out.

If the problem is specifically the corners of your mouth cracking and re-cracking, that is likely a different condition — a damp fold that has become infected, sometimes alongside a low iron or vitamin B12 level. That wants a doctor or pharmacist rather than another balm. One easy thing to try in the meantime, and people were emphatic about it: toothpaste containing sodium lauryl sulfate keeps it going for some people, and the sulfate-free kind sits right beside it.

And if your lips have been badly dry for months with no obvious weather to blame, that can be a side effect of medication or a sign of a deficiency, and it is a reasonable thing to raise at an appointment you were having anyway. For repeated splits down the middle of the lower lip, there are balms containing a mild steroid, sold over the counter in some places — worth asking a pharmacist about rather than ordering blind, since a steroid on the lips is not a thing to use indefinitely.

Back to the chair

One caution on the headline advice, from somebody who works in dentistry. A greasy film during active work is not ideal from their side — gloves and sharp instruments and slippery skin are a combination they would rather not have — and a firmer wax-based balm may be the better choice for the appointment itself.

Which is why the instruction is to put it on and then say so, rather than to put it on quietly. The person holding the drill gets to decide what is on your face while they work. What you are doing is making sure it is a decision somebody made, rather than something everyone forgot about until you got home.