How dirty are socks? Can they be washed with underwear?

For a long time, people have held the belief that underwear and socks should not be washed together in the washing machine because both are dirty and can easily cause cross-infection.

Actually, your worries are unnecessary. Why don't we need to worry? First, we need to understand what bacteria are on underwear and socks.

Bacteria on underwear and socks

After wearing socks all day, they usually have a pungent, sour smell and give the impression of being dirty. This is because feet are one of the parts of the body most prone to sweating. After sweating, bacteria on the skin use the organic matter in the sweat as food, metabolizing it into odor molecules, which naturally make the socks smelly.

Studies have found that worn socks mainly contain sweat, Staphylococcus aureus, fungi, and dead skin cells.

However, if there are no infectious diseases such as athlete's foot, the "dirt" on socks is mostly normal resident bacteria on the skin and their metabolites, which is not very harmful.

As for underwear, in some ways it is indeed much dirtier than socks! Although underwear is worn inside the body, it is in close contact with the reproductive tract and excretory opening. After a day of metabolism, it will retain sweat and secretions, and may even be stained with a little feces! In addition, the humid and warm environment will make it even more prone to bacterial and fungal growth.

Research by American microbiologists has found that an average pair of underwear contains 0.1g of feces, 1,000 parasite cysts, and as many as 10 billion bacteria and viruses, including Salmonella, E. coli, hepatitis A virus, and rotavirus.

So, will washing underwear and socks together cause cross-infection? See the next page!

Is there a risk of cross-infection?

Generally, washing socks and underwear together will not cause cross-infection. There are three main reasons for this:

Most bacteria on socks are common skin-degrading bacteria that also exist on other parts of the body. Even if they are transferred, they don't have a significant impact. Furthermore, these bacteria require a closed, moist environment to survive after being transferred, and generally cannot multiply in large numbers on other parts of the body.

If you use a washing machine, the vast majority of microorganisms will be shed from your clothes. Research from the University of Bonn in Germany found that washing clothes in 20.5°C water for 15 minutes can remove more than 95% of microorganisms. Furthermore, drying clothes in the sun or tumble dry after washing further eliminates microorganisms.

Even if a small number of microorganisms survive, our skin will act as a barrier to prevent their invasion.

Therefore, washing underwear and socks together is generally not a big problem.

However, in two special circumstances, it is still recommended to wash them separately!

When hand washing is the only option

Whether it's the time and force required to wash clothes or the final level of cleanliness, hand washing is far inferior to machine washing.

Studies have found that washing machines using 30°C water and regular detergent for a 45-minute cycle can kill 99 percent of bacteria. In contrast, hand washing is not as effective at eliminating bacteria.