Your hair is naturally more fragile when wet, and a full night of sleep is often accompanied by tossing, turning, and generally tugging your hair across the pillow, hence the knots you wake up with. When your hair is dry, breakage will be more minimal, but regularly sleeping with wet strands can almost ensure hair fallout when you sleep as your hair is tugged from side to side.
“The hair is weakest when it's wet, and as you toss and turn throughout the night, the friction can cause the hairs to more easily break,” warns clinician Dr. Paula Morgan, MD, PhD, FRCPC, FAAD. “Because the hair cuticle opens when wet, the hair becomes more stretchy and brittle. When the hair cuticle is exposed, it can stretch more, which might cause the hair to break more easily,” adds Dr. Sam Elmais, aesthetic dermatologist and founder of Medlink Students.
Not only can sleeping with wet hair cause breakage, but it may also exasperate any existing scalp issues and irritation, especially as the dry weather of the winter approaches. “Going to bed with damp hair can also increase the chances of fungal infection on the scalp, which can in turn lead to problems like dandruff and dermatitis. On top of that, it can also negatively affect the appearance of the hair, flattening strands, giving it an unpleasant odor, and leaving it a frizzy mess,” explains Morgan.
You also open yourself up to the chance of your hair drying poorly, and waking up with a deflated or dented look which can be difficult to remedy once it has dried that way.
If at all possible, try to give your hair at least an hour at night to air dry before going to sleep in order to avoid applying heat to your locks. However, if you’re in a time crunch you will ultimately be better served blow drying your hair before bed than falling asleep with it wet.
Another option is throwing your strands into a loose braid or two--just make sure to avoid pulling too tightly as wet hair is notoriously more prone to breakage, even during styling. A loose bun tied with a scrunchie rather than an elastic is another option to preserve your strands while you sleep. “Scrunchies, especially silk scrunchies, are significantly gentler on your hair,” notes Elmais.
Protecting your hair by avoiding sleeping with it wet is essential to achieving a good hair day, everyday. However, taking styling precautions and even using silk pillowcases can be more gentle on your strands if you do find yourself with no desire to air or blow dry it before bed.
Just remember, your hair is incredibly fragile, and preserving it from breakage with your sleeping habits will ultimately serve you well down the road for maintaining envy-inducing locks for years to come.