You may think it is just part of foreplay to get your girlfriend in the mood.
But treating her to a little oral sex might just be good for your health, as well as your sex life.
So much so that it could help cure your eczema, allergies and stop you getting fat.
So what are you waiting for, boys? Get down to it.
All the science all rests on the fact the vagina is full of good bacteria, called lactobacillus, which helps women fight off bad bacteria that can cause problems down there.
Vaginal discharge is also the body’s natural way of cleaning itself, which is why gynaecologists recommend women only use warm water to wash their bits – because it doesn’t upset the good bacteria.
Lactobacillus is a type of probiotic bacteria found in our digestive tracts, urinary and genital areas.
But it doesn’t just protect us from bad bacteria.
It is used in products to to treat diarrhoea, general digestion problems, irritable bowel syndrome (IBS), ulcers, urinary tract infections, thrush and the common cold in adults.
It has also been used for skin disorders like mouth ulcers and eczema, according to Web MD.
Probiotics, or levels of good bacteria in the gut, are even thought to help us lose weight.
So how much of this good bacteria is in vaginal fluid?
And how much would you have to, well, swallow to see any health benefits.
The answer is quite a lot – and it is probably unlikely to give you enough good bacteria to promote better health, Dr. Helena Mendes-Soares of the Mayo Clinic told Vice.
She said: “I think it would be possible, but probably unlikely.”
According to Helena there is anywhere between 100,000 and 100 million lactobacillus bacteria per gram of vaginal fluid.
So that would mean you’d have to swallow between 10 and 10,000 grams of vaginal fluid in one oral sex session – which would require a marathon foreplay sesh.
But even if you manage ten grams, do probiotics work?
Now, you’re probably thinking that a probiotic is something found in yoghurt or supplement, and not something you associate with getting down and dirty in the bedroom.
But probitoics naturally occur in live bacteria and yeasts – you can even get probiotic beer.
They are often added to yoghurts or taken as food supplements that are thought to help restore the natural balance of bacteria in your gut.
However, there is still some debate about how beneficial they are to our health.
A 2010 study that compared the views of nine European clinicians found they agreed that certain probiotics were effective in reducing diarrhoea, IBS and digestive problems.
But also found that evidence for them being used to treat eczema was “promising but inconsistent”.
A 2016 from Novo Nordisk Foundation Centre for Basic Metabolic Research at the University of Copenhagen found that probiotics have no effect on health adults.
They looked at more than 1,000 studies that tested seven probiotics and they found that only one of them found a difference between the gut bacteria in people that were taking a probiotic and people that weren’t, and even then it was only slight.
On the other hand, Dr Mark Hyman, the director of the Cleveland Clinic Center for Function Medicine, said that probiotics do work.
“Along with other gut-healing nutrients, a low-glycemic, whole foods diet filled with healthy proteins, fats and fiber, and probiotics can improve the health of your gut significantly,” he wrote on his blog.
“Why? Because probiotics help to populate your gut with good bacteria.”
And that good bacteria helps fight of bad bacteria when we come into contact with it.
A healthy gut is essential to a healthy lifestyle.
But it is important to remember that there have been no actual scientific studies into whether going down on your girlfriend is a sufficient source of probiotics.
But, in the meantime… it can’t do any harm – and you’ll get a whole load of brownie points.