We have bacteria living on our skin. But that’s not all, is it?

No. We have about 1,000 different types of bacteria that dwell on our skin in different populations and different people. But we also have different types of mites of varying degrees of ugliness, and one of my favourites is called a Demodex mite. It is a really horrible-looking mite: it looks like the cross between a worm and a spider. They’re present on the skin of quite a lot of people, and they tend to cling to the bottom of hairs, usually around the face.

At night, the males swim sluggishly across the surface of your face, searching for a mate. They have quite sad and short lives really. They’re good cleaners: they eat dead skin on the surface of our faces. But because these little mites have quite a small digestive tract and they don’t have an anus, they keep on hoovering up the skin, and eventually they get more and more bloated until they effectively burst and die.

Demodex mites chomp on your skin flakes, then explode © Getty Images
Demodex mites chomp on your skin flakes, then explode © Getty Images

While they are good at cleaning up the debris on our skin, they actually contain bacteria within their microbiome, and there are some theories that suggest that once these mites die and their gut microbes splurge out onto our skin, we can react quite badly to them. That could be one cause of rosacea, which is a reasonably common skin condition that exhibits itself as redness around the nose and just below the eyes.

Our discoveries into the skin microbiome are really interesting. A 2017 study found that an underarm bacterial transplant could potentially be the cure for body odour (BO). So, they got a pair of twins, one of whom smelt pretty fresh, the other of whom had quite bad BO, and they hypothesised that it was due to different populations of microbes.

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Our sweat doesn’t smell, but it’s the bacteria that digest the sweat and create smelly molecules that contribute to BO. So, in this study, they got the twin who didn’t smell to refrain from washing for a couple of days, then they swabbed some of his underarm skin for the bacteria. Then, they scrubbed the armpits of the slightly whiffy twin and placed his twin’s microbes on his skin, and amazingly, after weeks and weeks, both twins didn’t smell at all.

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That’s backed up by studies that show that people of East Asian heritage, particularly Koreans, have the least amount of body odour of any humans, and that’s because they, for various different reasons, have very small to negligible populations of the smelly bacteria Corynebacteria.

We often risk skin damage when we try and get a tan. Is there a safe way to get a ‘healthy glow’?

A couple of studies have been done over the last 5 or 10 years that have shown that if we eat colourful fruits and vegetables – like carrots, peppers and tomatoes – it gives our skin a yellowish glow.

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In one study, men were split into different groups, and one group was encouraged to eat colourful fruit and veg, and then women were asked to judge the attractiveness of the men’s faces. They found that the men who had this slight golden glow from eating colourful vegetables as part of a balanced diet were deemed more healthy and attractive than people who didn’t eat these, and also people who had a glow from a suntan.

What signs of skin damage should I look out for on my skin?

It’s important to check your skin regularly, getting to know where the moles are and to see whether there are any kind of changes.

The big thing to look out for is potential risk of melanoma, which is one of the three main types of skin cancer. It’s the rarest, but it’s also the most dangerous. There’s an easy way of recognising these on your skin, and it’s helpfully categorised into an ABCDE.

  • A is for asymmetry. Most moles are fairly circular, so look out for ones that appear asymmetrical.
  • B is for border, so if it also has quite a squiggly, strange border, that’s important to note as well.
  • C is if it has more than one colour in it, so if you have a mole that has one bit that’s quite a dark black colour, and one side’s a bit red and a bit brown.
  • D is diameter. Look out for ones of over six millimetres. I know that’s quite hard to measure, but that’s roughly the rubber end of a pencil.
  • And then, importantly, E is both evolution – so how quickly it’s been growing on your skin, if you notice it growing over days or weeks – and, most importantly, E is for expert. If you’re just unsure about something, or if a mole on your skin looks a bit unusual, go to your local GP and get that seen to.
The outer layer of the skin, the epidermis, is formed from overlapping layers of skin cells © Getty Images
The outer layer of the skin, the epidermis, is formed from overlapping layers of skin cells © Getty Images

We try to have better skin, by moisturising, exfoliating, and taking supplements. Is this a modern behaviour?

Complicated and bizarre skin routines have been around for as long as we have. I’ve got quite a few favourite beauty routines of people historically. Princess Elizabeth of Austria made a cream from the spermaceti wax from the head of a sperm whale combined with almond oil and some kind of rose water. And then, at night-time, she slapped raw veal on her face and had a made-to-measure leather mask that covered the veal.

There are quite a lot of bizarre and faddish ways of trying to make skin look more attractive that come in and out of fashion. There are some that stand the test of time. So, Queen Cleopatra of Egypt, who was famed for her beautiful skin, had a stable of 700 donkeys who would provide milk in which she would bathe.

There is a little bit of science behind that. Some of the acids in milk and citrus fruit, alpha-hydroxy acids, have an exfoliating effect on the skin, making it look more fresh. There’s a bit of a debate as to whether that results in an anti-ageing effect, but there are a number of ways in which people try to either slow ageing or make skin more beautiful.

The Remarkable Life of the Skin by Monty Lyman (£20, Bantam Press) is out on 11 July.
The Remarkable Life of the Skin by Monty Lyman (£20, Penguin Books)

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.