When your date casually mentions his flossing routine, you tend to suddenly become self-conscious about your oral hygiene. When Brits, like myself, go to America, a similar thing happens the first time we use a public restroom: “What’s this tracing paper doing here? Why is it torn? Cripes! It’s a toilet seat cover! Why don’t we have these?”

But if a British statistician were to visit a toilet in the U.S., she might instead wonder whether a cover was necessary. Does it do anything, such as reduce the risk of disease (as opposed to improve comfort or boost your ability to produce origami gifts while peeing)?

Some evidence for:



Toilet-seat contact dermatitis. A paper published in the journal Pediatrics found “exposure to wooden toilet seats and associated varnish, lacquers and paints led to the development of an allergic contact dermatitis on the buttocks and posterior thighs.” It might not be a disease, but it’s probably uncomfortable. Toilet seat covers could reduce the risk of developing this type of dermatitis, but so could replacing wooden seats with plastic ones.

Neisseria gonorrhoeae. When an 8-year-old girl presented with a sudden onset of Neisseria gonorrhoeae, it merited a quick analysis in STI journal. The Australian doctor who observed the case thought the infection resulted during a long flight, when the child used toilet paper to wipe down a particularly filthy toilet seat and got her hands dirty. So, using a toilet seat cover, rather than attempting to clean the seat, could lower the risk of non-sexually transmitted infection (which is an “infrequent occurrence” anyway and affects more children than adults).

Functional bladder capacity. This is one just for the ladies. If, in the absence of toilet seat covers, women choose to hover, they could experience a “21 percent reduction in average urine flow rate.” Presumably, more women hovering could also result in more misses and dirtier toilets. That might increase the risk of infection, too.

Some evidence against:

Pretty much everything else. Public health professionals are continually emphasizing that it is virtually impossible to catch an STI from a toilet seat. It would require the perfect storm of bacteria (i.e. you would have to sit down on the exact place where the virus was deposited, immediately after it was deposited, and it would have to be a super virus that could survive outside the body).

That improbability is highlighted by a blog post on the Centers for Disease Control and Prevention’s website, which suggests that “if someone has an open, draining wound (MRSA positive) and sits on the toilet seat and does not wipe it, someone else can sit on the toilet seat and if they have an open wound contract MRSA, also.” The number of people with open wounds on the part of their bums that hits the seat is likely to be low. And of those people, the number with MRSA-positive wounds will be even lower.

Despite that, demand is high. One U.S. company that sells automatically dispensing toilet seat covers has 2,000 accounts in the Americas and takes in $5 million a year.

You can decide for yourself whether the covers are a low-cost way to minimize risk or an expensive waste of paper. But there is one other piece of research that might be relevant, especially if you’re a man. Between 2002 and 2010, doctors documented 8,959 incidents of “penile crush injury related to a toilet seat” in U.S. emergency rooms. We’re not sure how those happened — for example, whether most occurred sitting or standing — but we thought you should factor it into your decision about the seat covers.