This common heatwave habit ruins thin, mature hair, according to a trichologist

We get it. It's hot, you’re exhausted, and the last thing you feel like doing is switching on the hairdryer before bed. The air temperature is roasting enough as it is. And with the heatwave locked in for days to come, it’s seriously tempting to flop into bed with wet hair when you come out of the shower. What harm can it do?

Well, quite a lot actually. That’s the word from leading trichologist Mark Blake, who is urging us to avoid this lazy heatwave habit, especially if you’ve got mature or thinning hair. ‘Going to bed with wet hair is a very common mistake, and especially in a heatwave,’ he tells GH.

Don't go to bed with wet hair, leading trichologist warns

Firstly, hitting the pillow with soggy locks is inviting breakage. ‘Hair is weaker when wet than dry so you are more likely to damage it when you are asleep, tossing and turning on your pillow,’ he says. ‘If you’re older, your hair is already more fragile and especially vulnerable.’

And don’t think you’ve got a ‘get out of jail free’ card because you’re sleeping on a silk pillowcase. As Mark explains, leaving your hair wet can cause damage beyond the effects of friction.

Wet hair is more prone to damage

‘Your hair swells up and holds about 30% of its weight when it’s wet,’ he explains. ‘So if you leave your hair wet, you damage the cell membrane complex. That’s the bit that acts like a glue, holding the cuticles together. You’re stretching your hair from the inside.’ Which is not what you want for delicate hair.

Another consideration is what happens on your scalp if you sleep with wet hair. ‘Your scalp has around a million colonies of bacteria per sq cm living on it, and between 10,000-50,000 colonies of yeast living on it too,’ Mark warns. ‘Yeast and bacteria love damp, warm dark conditions so your bed becomes a breeding ground for them. The last thing you want to do is go to bed with damp or wet hair.’

Your hair swells when wet

As well as sounding gross, yeast and bacteria spell trouble for your hair health. ‘They impact healthy hair growth, and increase shedding,’ Mark explains. ‘This is even more of an issue for older women, as they also have drier scalps as well as weaker hair.'

Sleeping with wet hair could impact your hair health

‘Increased yeast and bacteria growth on a mature head can aggravate an already sensitive scalp and damage their fragile hair as well.'

Not wanting hot air on an already-hot head is quite understandable, but Mark says it’s a necessary evil for healthy hair. ‘Researchers have found blow drying your hair from 15cm away on a medium heat is less damaging that leaving your hair wet,’ he says. ‘So don’t be lazy – blow dry your hair!’