The discovery and subsequent ridiculing of a woman's used underwear has been broadcast on national television in an episode of Celebrity Big Brother. The incident saw male housemates sorting through some dirty laundry before coming upon a pair of knickers and exclaiming that they looked like they contained "pigeon s**t", before parading them to the other housemates and declaring: "We need to name and shame now."

Ofcom has since received 165 complaints about the incident but while some viewers were upset about the bullying of actress Stephanie Davis (the owner of the knickers), others seem to have joined in the general shaming, with news articles branding the moment "disgusting", "vile", and "vomit-inducing". It just goes to show that even in 2016, our knowledge and acceptance of vaginas (and their normal daily functions) is still ridiculously limited and stigmatised.

There are several issues at play here. The first is that, while most of us have a fair working knowledge of the anatomy and functions of a penis, we still treat vaginas as mysterious and embarrassing secrets. As a result, a quite astonishing number people aren't aware of the fact that a natural, healthy vagina self-cleans and emits discharge, produced by the cervix, which can change in colour, consistency and quantity from person to person and at different times in the menstrual cycle.

The second problem is that by treating this completely natural process as if it is obscene and disgusting, we are replicating deeply ingrained, archaic and misogynistic ideas about women's bodies being dirty and corrupted.

And thirdly, we are reinforcing the ridiculously widespread notion that a vagina can be altered and "improved" to better serve societal stereotypes (and, implicitly, men's needs). Just look at the recent news that women had to be warned about the dangers of putting balls of herbs marketed as "Herbal Womb Detox Balls" inside their vaginas.

Or the furore, just a week later, over "vagina tightening sticks" marketed as a way to "reduce or eliminate vaginal discharge" and to "feel tight and wanted again".

These products exploit damaging myths about the need to cleanse and "balance" vaginas (which are actually perfectly designed to stay healthy, clean and at the right pH level all by themselves, thank you very much).

They also have the potential to cause real harm, running the risk of abrasions, pain and infections, as well as an increased chance of sexually transmitted disease.

Quite apart from the blindingly obvious fact that shoving something bought off the internet into your vagina for a few minutes isn't going to have a major impact on its size and shape, (or indeed the truth that vaginas are completely awesome to have sex with in all their natural glory), why on Earth are we still policing, criticising and stigmatising women's bodies?

Why do we see tiny penis and balls pictures scrawled over every school desk, public toilet and student notebook, but never a cartoon vulva to be found? Why does Apple let you engrave the word "penis" on your iPad but not the word "vagina"? Why are we still paying a tax on tampons as a "luxury" commodity, while crocodile meat, marshmallow teacakes and houseboat moorings are apparently essential enough to remain tax free?

The truth is that shaming these completely normal bodily functions is just another tired, sexist double standard. We consider a sweaty, active man to be the peak of virile attractiveness, but a sweating woman to be worthy of a scathing headline. We celebrate and praise male body hair, but act like the same natural phenomenon on a woman's body is dirty and disgusting.

We're so freaked out by menstruation and female body hair that we'll show a woman shaving an already completely hairless leg in a razor advert, or use weird blue goo in a sanitary towel advert rather than anything that risks even remotely resembling menstrual blood.

These might seem like minor examples, but the stigmatisation of vulvas and vaginas has a cumulative and insidious impact, from the rapidly increasing number of young women having their labia surgically altered, to the millions of girls around the world who miss out on education because of menstrual taboos.

Undoubtedly, Channel 5 didn't help matters with the decision to broadcast the housemates taunting and shaming Davis over her bodily fluids in the name of "entertainment" but there are also things we can all do to help end the stigma around vaginas and menstruation.

We don't have to treat periods or vaginal discharge as disgusting or embarrassing. We don't have to act like the purchase of sanitary products is a humiliating ordeal (or a luxury treat, for that matter). And nobody has any excuse to stay in the dark about vaginas – there's plenty of information out there for those who choose to learn, whether you own one yourself or not.

Laura Bates is the founder of the Everyday Sexism Project, which has collated over 80,000 women's stories of harassment and discrimination at work and in everyday life.