Chafing is a mechanical injury. Skin moves against skin or fabric, moisture softens the outer layer and lowers its tolerance for that movement, and given enough repetitions the surface breaks down. Friction, moisture, duration. Everything that works acts on at least one of those, and everything that does not work is acting on none of them.

Which is why the most common suggestion — a dusting of talc — is the weakest one. It absorbs a little moisture for a little while, then cakes, and caked powder in a damp fold increases friction rather than reducing it.

Reduce the friction: barriers, and which kind

Anti-chafe balms in stick form are the workhorse. They are wax and silicone based, they stay put through a day of walking, they survive some sweat, and they do not migrate onto clothes the way a cream does. Apply generously to dry skin before the activity, not after the discomfort starts.

Petroleum jelly is cheap and works on the same principle, with two drawbacks: it is greasy on fabric and it traps moisture against the skin, which helps for a two-hour walk and works against you over a hot ten-hour day.

Silicone-based sports lubricants last longest and are the right answer for a long distance, a long shift or a hot holiday. They are also the least pleasant to wash out of clothing, so reserve them for when you need the endurance.

Reduce the moisture: the part everyone skips

An antiperspirant — not a deodorant, an antiperspirant, containing an aluminium salt — applied to inner thighs or under the bust at night is one of the most effective interventions available and one of the least known. Aluminium salts work by forming temporary plugs in the sweat ducts, the effect builds over several nights of use, and applying at night rather than in the morning is what makes it work, because the ducts are less active.

Do not put it on skin that is already broken. It stings ferociously and delays healing.

Fabric does the rest. Cotton holds moisture against the skin; synthetic athletic fabrics and merino move it away. This is the entire reason a cotton T-shirt is worse than a technical one on a hot day, and it applies to what is worn underneath as much as to what is visible.

Reduce the contact: shorts, and getting them right

A short worn under a skirt or dress removes skin-on-skin contact entirely, which beats any balm. The reasons people abandon them are all solvable. They roll up because they are too short or have no grip: buy longer, to just above the knee, with a silicone band. They are hot: buy a thin technical fabric rather than cotton jersey. They dig in at the top: buy a size up, because compression is not the point.

A long slip in a slippery fabric does the same job under a dress and is cooler, if a short feels like too much clothing in August.

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When the skin is already broken

Stop the friction first. Nothing heals while it is still being abraded, and a barrier product on raw skin is a comfort measure, not a treatment.

Clean gently with water, pat rather than rub, and let it dry fully. A thin layer of a simple barrier ointment protects it while it re-epithelialises. Zinc oxide preparations — the kind sold for nappy rash — are genuinely excellent here and cost very little. Give it air where you can.

See a clinician if it is weeping, spreading, ringed with an advancing red edge, hot to touch, or accompanied by a temperature. Broken skin in a warm fold is a good environment for bacterial and fungal infection, and both are straightforwardly treated once identified.

The signal that it is not chafing

A rash that is symmetrical, sharply edged, itchy rather than sore, or has small separate spots at its outer edge is more likely fungal than frictional. It will not respond to any of the above and needs an antifungal. A pharmacist can usually sort this out in a conversation, and it is a different problem wearing the same clothes.

What to have in the house

One anti-chafe stick in the bag you actually carry. An antiperspirant used at night through the warm months. A tube of zinc oxide ointment in the bathroom. A pair of shorts that fit properly and do not roll. That is the entire kit, it costs very little, and it settles the problem rather than managing it.