Biting your nails
Sucking your thumb or chewing your nails are dirty habits your mother probably scolded you about.
But, surprisingly, by putting your fingers in your mouth you’re actually helping to boost your immune system.
“People touch their mouths all the time and when they do they are naturally recycling microbes like bacteria from one part of the body to another, plus adding a few more,” says Prof Tim Spector, Professor of Genetic Epidemiology at King’s College London.
“We’re all far too scared of bacteria, but actually bacteria is our friend. The more you come into contact with, the more your body builds up an immunity to it, allowing it to protect you against the odd bad bacteria.”
So biting your nails may actually keep nasty colds and viruses at bay.
No one is suggesting you give up washing altogether, but long, hot showers can strip the skin of its protective layer of natural oils.
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“Dry skin conditions, especially in the young or elderly, can be caused by excessive bathing and showering in hot water and using harsh soaps,” says Dr Kannan Athreya, cosmetic dermatologist with healthcare
“Don’t worry about missing the occasional shower – it helps skin recover – and when you do have them, keep them short, turn down the temperature and use gentle products.”
Forgetting to brush teeth after a meal
Ok, so the person sitting next to you on the bus might not thank you for it, but not brushing your teeth straight after a meal is actually a good habit.
“Some foods and drinks encourage the production of a certain acid in your mouth,” says Dr Sameer Patel.
“The biggest culprits are citrus fruits and fizzy drinks, which attack your enamel. If you brush straight after eating you may force that acid further down through the layers in your teeth, accelerating the erosion process.”
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Brush at least half an hour after eating instead.
Not always washing your hands
Telling kids to wash their hands before dinner is something most mums insist upon, but it might not actually be beneficial to their health.
Professor Spector says: “Obviously, if you’re a chef it’s important to wash your hands before preparing food, but having a bit of dirt on your fingers when you’re eating isn’t going to kill you.
“In fact, it will just increase the amount of bacteria you’ve been exposed to and that’s a positive thing.
“It’s the same with eating food that’s been dropped on the floor. Some people use the five-second rule and I think that’s fine.
“We’re all obsessed with hygiene, but actually many of the microbiologists I know don’t even wash their hands in public toilets because they believe they’re more likely to pick up an infection from a dirty sink than from having some of their own microbes on their hands.”
Not making your bed
It seems teenagers were right all along – not making your bed is good for you.
“Dust mites favour the warm humid conditions that can be found in bedding and feed on your skin and sweat,” says dermatologist Dr Athreya, of Essex Private Doctors.
“Making your bed as soon as you rise incubates these favourable conditions and helps mites to thrive.
“The best hygiene practice is to aerate the bed by folding down the duvet to expose the mattress and fluffing up the pillows. Leave it a few hours before making the bed. This will air the linens and keep mites in check.”
Forgetting to use hand sanitiser
“Unless you’re preparing food on a cruise ship or in a hospital, you shouldn’t be using hand sanitiser,” says Prof Spector.
“Advertising leads us to believe we have to kill all known germs, but humans are not designed to live in sterile environments. By using antibacterial santitiser you are replacing valuable microbes with harsh chemicals, which can lead to allergies and weaken the immune system.
“Children under three in particular need a variety of bacteria in their bodies. Research shows that those who lack microbial diversity are more at risk from diabetes and obesity.”
“Gum is a great way to freshen breath and remove food debris from the teeth,” says Dr Patel.
“After eating, your teeth are more at risk of an acid attack from the sugars found in food and drink. Over time, this can dissolve the enamel of the tooth. Chewing gum helps stimulate saliva production, which is the mouth’s natural defence against acid. In turn that helps to reduce tooth decay.”
But make sure it’s sugar-free.
Not doing housework
If your kitchen looks like something TV cleaning gurus Kim and Aggie would baulk at, console yourself with the fact that you’re doing your skin a favour.
“No surfaces in the home need to be the 99 % clean TV ads tell us we should be striving for,” insists Dr Athreya. “When you overuse abrasive cleaning agents – especially if you have sensitive skin – you cause damage to the lipid part of the epidermis which is an important barrier for protection.
“Avoid harsh detergents and wear hypoallergenic gloves.”