If you live in a typical Filipino household, you’ve probably heard this from your mother: “Huwag kang matutulog nang basa ang buhok mo!” Chances are, she probably even told you that sleeping with wet hair will cause you to catch a cold or wake up with a nasty migraine.
Well, given that this article even exists in the first place, you probably already know where this is going.
The cold truth
Let’s start by debunking what is perhaps the most common misconception about this: No, you are not going to wake up with a cold just because you didn’t dry your hair before sleeping.
This myth likely stemmed from a misunderstanding of what actually causes colds. Colds are viral in nature; they’re not caused by low temperatures. It just so happens that the most common cold-causing viral agents, such as rhinoviruses, tend to thrive in cold environments. In other words, it’s not the temperature that makes us sick. It’s actually a bunch of factors present because (or in spite of) the chilly environment, all of which make it easier for the aforementioned viral agents to infect us.
(In fact, there are around 250 cold-causing viruses, which is the same reason why there isn’t an anti-cold vaccine yet; there are just so many cold viruses that an all-in-one solution doesn’t seem to be possible.)
An infectious rumor
Some say that sleeping with wet hair will cause fungal growth, seborrheic dermatitis (dandruff), and other scalp diseases and irritations.
Again, this is more of a case of misattribution than anything else. The wetness of your hair ISN’T what causes these conditions — it’s the presence of contaminants, spores, and bacteria in your pillow. Moisture CAN facilitate their growth and lead these potential problems to come to a head (pun intended). However, you’re actually better off making sure that your pillows and bed are clean than worrying about keeping your hair dry before bedtime.
Don’t make your head hurt thinking about this
Another interesting theory is that sleeping with wet hair causes headaches when you wake up. The explanation borders on pseudoscience:
The theory goes like this: blood tends to go to the parts of your body that are cold. If your head is cold, your body will divert more warm blood to your cranial region, and the built-up pressure will eventually cause you to get a headache. Others suggest that the difference in temperature between your hair and your body can make your head hurt, though they don’t exactly explain the mechanism behind it.
Long story short, there isn’t any scientific evidence to support this. Some people go to bed with wet hair and wake up feeling fine; others don’t. Same goes for people who claim that sleeping with wet hair causes blindness or even insanity: There’s absolutely no concrete evidence that either of those (frankly ridiculous) assumptions are true.
Why you wouldn’t want to sleep with wet hair
However, there’s ONE reason you wouldn’t want to sleep with wet hair, and it’s cosmetic in nature.
Hair shafts are weakest when wet. When you sleep with wet hair, you run the risk of damaging or even breaking it as it rubs against your pillowcase. Simply put, friction can cause you to wake up with some really mean-looking bed hair.
So no, you’re not necessarily going to get sick if you don’t listen to your mother. There’s a good chance, though, that when you wake up and look at yourself in the mirror, you’ll wish you did.
Cover photo: Gratisography
Author: Mikael Angelo Francisco
Bitten by the science writing bug, Mikael has years of writing and editorial experience under his belt. As the editor-in-chief of FlipScience, Mikael has sworn to help make science more fun and interesting for geeky readers and casual audiences alike.