Fetishes have been around for centuries — from the Marquis de Sade to Kinky Boots. But fetishes are about much more than shoes and leather.

Dear Lucy,

I am very turned on by raincoats but my wife is not keen. Do you have any advice?

Kind regards, Peter.

Peter* posed this question to an advice column of an online UK women’s magazine and got some handy marital guidance. But what does science have to say about fetishes? How common are they? What causes them? And if your partner doesn’t share your fetish, can science help?

Fetishes are not just about feet and leather.

When it comes to fetishes for body parts, nothing comes near feet and toes in popularity.

In 2007, the biggest ever study of fetishes found that the foot was way more popular than everything else, accounting for almost half of all fetishes.

Blood and other body fluids came a distant second, while tattoos and piercings were a clear minority, with body odour coming in dead last.

But if a penchant for BO seems unexpected, the fetishes for clothes or accessories were nothing short of eclectic.

Shoes and stockings still topped the list, accounting for two thirds of all fetishes.

But people registered sexual preferences for everything from stethoscopes and nappies to pacemakers.

Fetishes are rare — especially in women.

The world isn’t awash with research into fetishes — partly because fetishes are not enough of a problem to warrant funding, and partly because people tend to keep their sexual attraction to raincoats or hearing aids to themselves.

But across the studies that have been done, two things stand out. Fetishes are rare, and they’re almost unheard of in women.

A 1983 study on people diagnosed with sexual fetishism in a large London hospital found only 48 cases over a 20-year period. And of those 48, only one was a woman — a lesbian with a fetish for breasts.

In men who have clinical fetishism, the fetish usually develops at puberty and can vary in strength throughout life.

We don’t know what causes fetishes.

There’s been no shortage of theories — childhood trauma, epilepsy and even Freud’s ‘the foot looks like a penis’ idea — but we really don’t know what causes some people to form strong and lasting sexual attraction to unusual things.

Twenty years ago, neuroscientist V S Ramachandran suggested that foot fetishes might result from accidental cross-wiring in our brains. He based his idea on the map of the brain drawn up by surgeons in the 1930s — Penfield’s Homunculus — which showed that sensations in our feet map onto our brains right next to where sensations from our genitals do.

Associate Professor Michael Farrell from Monash University thinks it’s an appealing idea, but it’s probably a bit of a stretch, because “the maps are quite simplified compared to the reality”.

While there are rough divisions in the brain, they don’t correspond directly or exclusively to a single body part, he said. Our brain logic is definitely on the fuzzy side.

Another idea that was common before the 1960s was that temporal lobe epilepsy was linked with fetishes.

But Professor Mark Cook from Melbourne University says that was largely a result of the studies being done on psychiatric patients who had epilepsy.

“The link disappears once you start excluding people who have an obvious psychiatric diagnosis,” he said.

So for now, we still don’t know what’s behind a sexual attraction to hats or hearing aids.

Foot fetishes are linked with STDs, but not how you’d expect…

Throughout history erotic art and writing have focused on the usual suspects — women’s breasts, backsides and thighs.

But every now and then women’s feet suddenly got sexy. And by every now and then, I mean whenever there was an epidemic of syphilis or gonorrhoea.

A study in 1998 found that foot fetishism in books, poetry and paintings coincided with each of the four major STD epidemics since the 13th century.

And foot porn went through the roof with the arrival of AIDS.

As with the earlier epidemics, foot fetishism should drop off with the easing of the AIDS epidemic — but no-one seems to have done that follow-up study just yet.

Fetishes are not usually a problem.

Getting turned on by a raincoat or a handbag might be unusual, but in psychiatric terms fetishes are only a problem if they really mess with your life, or the lives of those around you.

According to the latest version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), your fetishistic sexual urges have to last for at least six months, cause distress or impairment, and not be for something obvious like a vibrator.

Tick those boxes and you could be clinically diagnosed with fetishistic disorder. Which isn’t great news because not only would your fetish clearly be making life hard, there’s no guaranteed treatment for the disorder.

There are treatments, but we don’t know how well they work …

If a fetish is problematic, the treatment options boil down to either changing behaviour (through cognitive behavioural therapy) or reducing sex drive with drugs or hormones.

The research tends to be one-off reports of successful treatment of a particular patient, so there’s no clear picture of how well — or for how long — those therapies work.

*Peter — if you really do exist — listen to the first episode of Dear Science and you’ll get more raincoat-lovin’ advice, courtesy of your scientific agony aunts Bernie Hobbs and Dr Alice Williamson.

This post originally appeared on ABC News.