Human hair is a complex thing. Each strand consists of several layers which contribute to the structure, shape, and color of the hair. The outer layers are made of several tiny keratin scales (cuticles), which overlap like shingles. The core (cortex) of the hair strand consists of bundles of long, thin cells that contain melanin, the hair’s natural pigments. The hair also contains lipids, or fats, which balance moisture. Additional lipids are deposited onto the surface of the hair via the scalp’s sebaceous glands.
Healthy hair does pretty well at maintaining its own moisture levels. The sebum and keratin on the surface of the hair provide a hydrophobic barrier to prevent excess water from entering the cortex. It may sound counter-intuitive, but too much water is not good for the hair. If water enters the center of the hair strand, the cortex swells and the overall structure of the hair weakens. This is why hair becomes stretchier when wet. Healthy hair will stretch to an extent, and bounce back. Hair that has been damaged will remain stretched, and break if stretched too far.
On the other hand, if the cortex is completely depleted of moisture, the hair becomes brittle, and breaks. Think of the cortex like a bundle of al-dente pasta. If it soaks up too much water, it becomes mushy and unstable. If it is desiccated, it becomes brittle and snaps.
Hair is made of a bundles of cortical cells containing melanin, surrounded by keratin scales.
Maintaining healthy hair requires keeping the keratin layers as intact as possible. When new hair growth exits the scalp, it has several layers of keratin cuticles which are tight and flat. Normal weathering causes the cuticles to lift, then chip away. If most or all of the layers erode, the cortex is exposed, and it unravels like the end of a rope. This is what causes split ends, also known as trichoschisis. There is no way to “fix” split ends, except to trim them away with professional shears (regular scissors can cause split ends). You cannot glue the cortex back together and put a new coating of keratin over it. Maintaining healthy hair is all about being proactive, not reactive. There is nothing that can reverse damage once it has occurred.
When keratin cuticles are entirely weathered away, the cortical cells are exposed and eventually split.
The biggest outside threats to hair health are friction and pulling (especially when the hair is wet), heat, UV exposure, and chemical processes. Friction causes the cuticles to lift, making the surface of each strand rougher. Strands then catch on each other, causing tangles. Lifted cuticles are like open doors for water to pass in and out. This is why damaged hair is stretchy and mushy when wet, and brittle when dry. Heat drys out the hair and causes air pockets within the hair strands to expand. UV radiation breaks down melanin cells and melts the hair’s cortex, making it porous and brittle. Lightening agents, oxidative dyes, perms, and relaxer all use chemicals to break through the keratin layer to permanently alter the cortex to deposit dye, destroy melanin cells, or force the hair into a new shape. This creates weakness in both the internal and external structure of the hair.
While some weathering is normal and expected, there are many ways to reduce the amount of day-to-day damage. Here are a few ways to keep your hair happy and silky.
1. Squeeze and Wrap; Don’t Rub.
After showering or bathing, you might be tempted to grab a towel and rub it all over your head, or rub your hair between your towel like you are trying to start a fire with a stick. Don’t do it. Your hair is extra fragile when wet, and this amount of friction will add up in the long term. Repeated towel drying contributes to the weathering of the keratin scales that form the protective outer layers of the hair. Over time, this will lead to split ends .
Instead, gently press or squeeze your hair with the towel. Wrap your hair with the towel and allow it to gradually absorb the water out of your hair. Or gently shake the ends of your hair to flick away water droplets.
2. Don’t Brush Wet Hair
This is similar to towel-drying the hair. Brushing, towel drying, and any form of friction on wet hair causes keratin cuticles to shed. Wet hair has reduced tensile strength, meaning it is more prone to stretching and snapping than dry hair. A study found that using a conditioning shampoo, in comparison to non-conditioning shampoos, reduced the amount of cuticle loss during wet hair combing . This would make sense, as shampoos cleanse away the natural lipid layer of the hair, and lift the cuticle, increasing friction.
If you must comb your hair while it is wet, make sure the hair is conditioned, and use a wide-toothed comb, or a brush specially made for use on wet hair. Work from the ends of your hair to your roots. Do not pull on a tangle. This will cause your hair to snap. Work out the knot from the bottom up.
Hair and drum skins are both made of keratin. Kitty’s drum got wet and it wouldn’t play anymore. So kitty tightened it. But when the skin dried, it tore. Oops! Poor kitty. Shouldn’t have stretched a wet drum.
3. Keep Your Hair Up
Loosely braiding your hair or keeping it in a twist protects it from friction and tangles during the day. This is especially helpful if you have long hair and it’s a windy day. Just be sure not to wrap hair ties too tightly, or force pins into a tight bun.
(Writer’s note: Back when I had long hair, I was a big fan of the octopus clip. It securely holds the hair up in a bun without pinching, or being too tight.