Bleach Bio

I've been bleaching my hair for a while now, and while I love the way it looks now, learning how to bleach it properly and keep it healthy has left me with more than a few bad (maybe closer to horrible) hair days, or even weeks. I've been over that for a while now, but these are all things I wish I understood when I started bleaching and coloring my own hair!

All visible hair cells are already dead, produced by the hair follicle within the dermis at the root. Some cells under your skin are already dead, but the hair matrix is an area of mitotically active (so they're alive) basal cells. That's why saying "dead ends" or that bleach kills your hair isn't really correct. These dead cells are keratinocytes, and have undergone a special type of apoptosis called cornification. After enough keratin has built up in the cell, the cell's organelles are ejected. The core of the hair shaft is the medulla, which is surrounded by the cortex, containing cells that are the majority of the shaft and its pigments. The cortex is made up of long keratin filaments that are held together by disulphide and hydrogen bonds, structural lipids, and dead cells. The outside of the hair is encased by the cuticle, having the main function of protecting the cortex. When the cuticle is healthy it's shingles of dead cornified cells lie flat, protecting the cortex, but when chemical processes like bleach disrupt it and raise the cuticle, hair can become brittle and not be able to retain moisture.

Picture I drew of the cross section of the hair shaft

Coiled Structure of Keratin

Hair Shaft and Root

Bleach is an oxidizing agent and removes color from hair and fabrics by releasing oxygen from chromophores, parts of a molecule that reflect color, and pigments. The oxidation breaks up chromophores and pigments so that they reflect colors outside of the visible spectrum, or no color at all.

Hair Bleach (H2O2+CaCl2) can only break down hair’s pigments by lifting and moving past the cuticle. Moisture and water from a shower can slightly lift the cuticle, but products like bleach and hair relaxers with a pH higher than 5.5 lift the cuticle completely. With the cuticle raised bleach enters the cortex and is able to oxidize melanin, a group of pigments that gives color to human skin, hair, and eyes. This makes hair lighter! While this happens bleach is simultaneously destroying the bonds within keratin and breaking down natural fatty acids. This means that while your hair is getting lighter it is also getting weaker. Going too light too quickly often results in fried hair, or hair becoming so weak it breaks off. To help replenish fatty acids or give the appearance of healthier hair, instead of buying fancy treatments plain oils like shea or jojoba are great! This works pretty well for long hair with "dead" ends as well, but unfortunately there is no fix for split ends.

Sometimes after too much bleaching or chemical treatment hair becomes extremely stretchy, or even slightly sticky when wet. This is caused by keratin leaching from within the cortex, reducing the amount of keratin and weakening hair enough to stretch more than is healthy or normal. The different types and quantities of melanin present in different hair colors affect how they react to the same bleaching. Blonde and light brown hair get lighter and yellow much faster because they already have little melanin. Black hair turns more orange when bleached for the first time because it has eumelanin (brown pigment) and pheomelanin (red pigment) and pheomelanin is broken down after eumelanin.

I've had stretchy hair, hair that seems dry beyond repair, and extremely patchy orange and brown.  After all the different hair issues and colors i've been through here are some of my favorites!