Boxers, briefs and bacterial vaginosis: how your underwear can affect your health

Thongs, briefs, long johns, g-string, boxers, trunks: there’s a bewildering array of undies out there. But which ones are best for the health of your nether regions?

Well, the style of underwear you choose is less important than the material it is made of. Natural fibres such as cotton are far better for the skin, especially the sensitive areas around the genitals, where breathability of the garment is important.

But, even if your pants drawer is full of cotton briefs, you’ll still need to be wary of fit, dyes and dirt. Here’s what women and men need to know about the links between their underwear and their health.

For those who have one, it’s important to remember the vagina is a self-cleaning organ. It produces up to 5ml of fluid per day and has a balanced microflora consisting of many different bacteria – although it’s typically dominated by those of the lactobacillus genus.

These bacteria produce lactic acid which ensures the vagina maintains the correct, typically slightly acidic, pH, reducing the risk of infection.

There’s limited research on how underwear style might impact vaginal health. The most notable study, though, found that thong-wearers were more likely to report urinary tract infections (UTIs), vaginal yeast infections and bacterial vaginosis.

However, it may not be the thong itself that causes infection: in the study, UTIs were associated with oral sex and bacterial vaginosis was linked to non-cotton crotch underwear.

Bacterial vaginosis is a dysbiosis – a bacterial imbalance – in the vagina that can be caused by non-breathable underwear. Synthetic fibres, and the dyes used to colour them, can alter the conditions of the vagina leading to a sub-optimal conditions for good bacteria (such as lactobacilli) to exist.

Synthetic, dyed underwear can cause pH levels to increase to over 4.5 allowing anaerobic bacteria to thrive and lactobacilli to perish. These conditions can lead to bacterial vaginosis, or an increase in the growth of fungi such as candida albicans, causing thrush.

However, it seems that wearing tight-fitting clothing, including underwear, over time may increase candida levels in the groin.

Underwear that is too tight fitting can also cause friction and irritation around the genitals. This can result in anything from skin tags (which may look like genital warts depending on their location), ingrown hairs and blisters.

Forget the budgie-smugglers

In men, the testes are the primary site of sperm production. They hang away from the body to achieve a 2°C-4°C cooler environment. Testicular temperature is so important that the body has its own means – the pampiniform plexus – to cool the arterial blood as it flows into the testes.

There is scant research on the exact effect of underwear type on sperm quality and quantity. However, research found that those who reported frequent wearing of boxer shorts had a higher sperm concentration than those who wore other types of underwear. Boxers, also demonstrated and maintained a reduced scrotal temperature.

There’s also research to show that increased scrotal [temperatures] in men from a variety of contexts and occupations, resulted in marked reduction in sperm count for weeks. Thankfully, in most settings sperm count is recoverable.

The impact across a number of weeks is likely because it takes approximately 74 days for a sperm to be born and reach maturity with ability to exit the body, and temperature can affect sperm at any point in its journey.

However, men who undergo vasectomy are advised to wear tight fitting underwear for at least 48 hours and up to seven days post-operation. The tight fit helps support the testes, reducing their movement and the strain on the very thin layers of fascia and muscles that cover the testes. Movement results in pain, as well as a risk of opening any wounds, and increases the chances of infection.

Keep it clean

Cleanliness of the body and the underwear is essential for everyone. Research shows that even clean underwear can contain 0.1b-10g of faecal matter, and those bacteria have the potential to make you ill.

Avoid brightly coloured underwear, choose natural fabrics and wash them regularly to keep your genitals happy. DenisProduction.com/Shutterstock

Cleaning the skin, as well as your underwear, reduces the potential for fungal infections too, such as tinea cruis, sometimes known as jock itch.

This red or brown itchy rash is four times more common in men than women. Athletes typically present with fungal infections in their groin from increased heat and sweat generated while exercising. Sportsmen tend to develop the infection along the crease between the scrotum and thigh because of the tight-fitting underwear worn during contact sports.

You can go commando – but take care with zips

Foregoing the barrier underwear creates between sensitive areas can actually be beneficial. Going commando enables air to circulate, allowing secretions to dry naturally, reducing the moist conditions that can contribute to infections.

The main risk of going underwear-free seems to be for men who’re careless with trouser fastenings. Injuries from zip fastenings almost always involve men damaging their penis or scrotum.

So, picking natural, breathable fabrics – and perhaps button-fastenings – are best for health down there. And always remember, if something doesn’t look or smell right it is best to get it checked out.