Is there any truth to the idea that underwear should be purchased annually?

Some bloggers and underwear sellers claim that underwear should be replaced every 6-12 months. According to them, even if the underwear is regularly washed, harmful bacteria can accumulate over time, which can lead to infection. However, there is no serious scientific basis for these recommendations: if you wash your underwear properly, there is no need to worry about bacteria accumulation. Therefore, if the underwear has not worn out within a year, it can continue to be worn.

Where do bacteria in underwear come from and how dangerous are they?

Usually, only bacteria that already live on the surface of the skin or inside the human body, such as bacteria and fungi from the skin surface, mucous membranes, and feces, end up on underwear.

Some of these bacteria, such as golden staphylococcus and E. coli, can live in the intestines and not cause problems in healthy people. But if they end up on clothing in large amounts and from clothing to the vagina, urethra, skin wound, or mucous membranes of the nose or eyes, they can cause infection.

There is indeed a risk that bacteria will begin to accumulate in clothing, as clothing creates a warm and often moist environment on the skin, which promotes bacterial growth. Moreover, bacteria can survive on clothing for quite a long time.

On cotton fabrics, golden staphylococci remain viable for up to eight days, and on fabrics made of mixed fibers, for up to 41 days. E. coli can survive on these materials for even longer – up to 45 days. Both types can survive on synthetic fabrics for up to 206 days.

But based on the data available to us, regular hand washing is much more important for preventing most dangerous infections than washing clothes. This is because we obtain most dangerous bacteria either by interacting with infected people or by touching surfaces contaminated with these bacteria. Pathogens of infectious diseases from the external environment usually do not end up on underwear.

Can you get sick from underwear that has been worn for more than a year?

To this day, there has not been a single case of people getting sick from old underwear that has been worn for years and regularly washed. Moreover, no authoritative international medical recommendation recommends getting rid of underwear after a year of use. Most likely, this is because the number of microbes in the fabric is effectively controlled by regular washing.

Studies show that washing clothes at a temperature of 60°C and above helps to deal not only with intestinal bacteria but also with microbes living in hospitals. However, washing at such a high temperature is not suitable for some delicate and colored fabrics used in expensive underwear.

But this is not a problem either, as modern detergents with bleaching activators help to eliminate most of the microbes at low water temperatures. And the small amount of microorganisms that can survive washing and linger in the fabric does not lead to health problems because there are too few of them.

All of this means that underwear does not have an expiration date. If it still fits after a year or more, has not torn or lost its shape, it can still be worn.

How to properly wash underwear

To get rid of bacteria without damaging your underwear, it makes sense to follow safe washing rules.

White cotton and linen underwear should be washed at a temperature of 60°C or higher, as the hot setting is the safest from a medical point of view.

Colored underwear made of most fabrics, such as cotton, acrylic, and a mixture of natural and synthetic fibers, should be washed at a temperature of 40-50°C, otherwise it may lose its color. But since this temperature range is not as effective in killing bacteria, it makes sense to wash it with a detergent that contains tetraacetylethylenediamine (TAED) bleach activator and oxygen-based agents. Oxygen-based agents react with TAED to form a powerful antiseptic – peracetic acid. Such detergents are suitable for both colored and white fabrics.

Silk underwear is recommended to be washed in cold water, i.e. at a temperature of 30°C or below. At temperatures below 30°C, TAED-containing products are not as effective as at 40-50°C. However, there has been no known case where people who prefer silk underwear have gotten sick because of bacteria accumulating in it over time. Most likely, with regular washing, such underwear is no less safe than cotton or mixed fiber underwear.