Heat rash when it is warm

Short answer: Small red spots in skin folds and under tight clothing appear when the sweat ducts are blocked. Loose, smooth fabric prevents it.

What happens in the skin

Sweat cannot get out through the skin because the duct is closed by moisture, friction or a layer lying too close. The sweat stays below the surface and gives small itchy spots.

Where it typically sits

In skin folds, under a waistband, under a bra and on the back where the fabric lies tight against the chair back. See bamboo underwear for women.

How to avoid it

Loose, thin clothing that lets air reach the skin. Change into dry clothes when you have sweated. Bamboo viscose moves the moisture away rather than holding it. See bamboo t-shirts for women and bamboo activewear for women.

Frequently asked questions

Does it go away on its own

Yes, once the skin is allowed to be dry and cool for a few hours.

Does powder help

It can keep the skin dry, but it can also block the ducts further.

Why does it affect the back

Because the chair back stops air from reaching the fabric.