Ask the Expert: Can tight underwear lower sperm count?

This is one of those questions that is answered all over the internet and a good example of why you shouldn’t believe everything you read.

Your testes hang away from your body for good reason — normal body temperature (about 37°C) is too warm for optimal sperm production. In humans, the temperature in the scrotum is about 1.5-2 degrees lower than your body temperature. Some have speculated that tight underwear pushes the testes closer to your body, warming them to a point where sperm production is affected.

But contrary to what your Google search tells you, there is no good evidence that wearing tight underwear causes you to have a low sperm count. The studies that are often cited, even by supposedly reputable sources (like New Scientist) are usually conducted in groups of men who are seeking help for fertility problems, so you can’t generalise the results to the whole population.

One of the best quality studies¹ of ‘boxers versus briefs’ included measurement of the temperature of men’s scrotums: they weren’t different. Their sperm counts weren’t different either.

Some of the studies that supposedly show the effects of different types of underwear on sperm counts use the wrong methods for comparing data or are based on cherry-picking of data that show an effect while ignoring the data that don’t. Other studies are too small to be reliable, or there are so many variables in the study that it’s impossible to know whether underwear or something else is responsible for any differences between groups of men.

There’s even less evidence for an effect of underwear on blood flow to your testes or penis, or for an increased prevalence of genital infections in men who wear tight undies.

Myths about the effects of underwear on men’s fertility and sexual health are so probably so prevalent because they make sense. They’re based on the reasoning that we can understand and offer a simple solution to complicated problems: just change your undies.

The problem is that misinformation about simple, but unproven, solutions to things like infertility and erectile dysfunction can prevent people from seeking help for these serious and complicated problems.

If you think you have problems with infertility, erectile dysfunction or genital infections, see your doctor before you worry about changing from briefs to boxers.