The elastic in your underwear has gone slack and why that happens

Short answer: Elastic gives out when it is exposed to heat, chlorine and fabric softener. Wash at low temperature, skip the fabric softener, and let the waistband dry without hanging under its own weight, and it lasts markedly longer.

Heat is the worst enemy

Elastic is rubber or elastane wrapped in yarn. Heat makes the material lose its stretch, and that happens both in the washing machine and in the tumble dryer. A pair of underpants that is regularly tumble dried on high loses its waistband in under a year. See bamboo underpants for men.

Why low temperature makes a difference

The same pair can last several years if washed at low heat and never put in the dryer. The difference is not how often the pair is worn, but how many times the elastane is exposed to high heat, because each time it weakens the fibres a little further, no matter how well the pair otherwise fits.

Fabric softener and softening agents

Fabric softener coats the fibres in a film and makes the elastic slick and sluggish. It feels softer the first few times and then goes slack. Use a plain detergent with no additives, and skip fabric softener for underwear, even if you use it for other laundry in the household.

Chlorine attacks elastane directly

Chlorine and bleach attack elastane directly and cause permanent damage, unlike heat, which acts gradually over many washes. Even a single splash of chlorine from another load can noticeably weaken a pair of underpants, so keep them well away from laundry that is being bleached.

How to treat the waistband

Never pull a wet pair up by the waistband when hanging it to dry, since the weight of the wet fabric pulls directly on the elastic. Lay it flat or hang it over the line at the middle, so the weight is not concentrated in one spot but spread evenly.

Do not fold the waistband over

Do not fold the waistband over when putting clothes away, since a permanent crease in the elastic does not come back out. Instead fold the pair so the waistband lies flat and unfolded, and store it without squeezing it between heavier items in the drawer.

When the elastic is worn out

When the waistband no longer pulls back together after being stretched, the elastane has broken down and cannot be saved. That is the point at which a pair should leave rotation, since a slack waistband slides and causes discomfort all day no matter how well the rest of the pair fits.

See the range for replacement

See bamboo panties and bamboo underwear for women, where the material in the waistband is chosen to last with proper care, and where you can find a new pair ready to take over once the old one needs replacing.

How to keep several pairs in good shape at once

If you have several pairs of underwear, rotate them instead of washing the same pair again and again, since that gives each pair more time between each exposure to heat and moisture, which markedly extends the lifespan of all of them.