Whether for making a fashion statement or just for covering grey hair, people have been using hair dye for many years. One year, blonde hair may be popular, the next year it’s brown hair. The definition of beauty is always evolving.

Where did this fad come from?

People have been dying their hair for centuries! Ancient Greeks used harsh soaps and bleach to lighten and redden their hair. The Romans used boiled walnuts and leeks to darken their hair. In 1909, a French chemist, Eugène Schueller, created the first commercial hair dye. His creation led to the foundation of his company, L’Oréal.

Where does your natural hair colour come from?

Imagine that a strand of hair looks like snake skin, with lots of overlapping “scales”. The scaly outer layer of a strand of hair is called the cuticle. The cuticle protects the inner layers of your hair, which is where the pigments that determine your hair colour can be found.

There are two types of pigments in hair: eumelanin (which has two subtypes, black or brown) and pheomelanin. The relative proportions of eumelanin determines how dark (or light) you hair is, while the type of pigment determines its colour. People with higher levels of pheomelanine will have red hair and those with low levels of brown eumelanin will be blond. As people get older, hair loses its pigmentation, causing it to turn white or gray.

So how do hair dyes work?

The two most common types of hair dye are temporary and permanent. Temporary hair dye cannot penetrate the tough, outer cuticle layer and only attaches to the surface of the hair. Since this dye does not reach the pigments, it easily washes out after a few shampoos.

Permanent hair dye generally contains ammonia and hydrogen peroxide. The ammonia in the dye mixture causes the hair to swell up so that the dye can penetrate the cuticle layer and reach the pigments. Some companies have now using alternative chemicals to ammonia that are odourless. The hydrogen peroxide in the solution then reacts with the pigments to lighten the hair’s natural colour and allow the new colouration to show. This is why you have to wait once the dye has been applied to your hair so that the hydrogen peroxide has a chance to let the colour develop.

As beauty continues to evolve, we can expect to see more outrageous and colourful uses of hair dye to express and represent our individual personalities.


Hair Colouring.Chemical & Engineering News: What’s that Stuff? Vol 78(11): 52. March 13,2000.

2006 CRAM Science article on hair dye

HowStuffWorks: How Hair Colouring Works

Hair Boutique: Non-Toxic Hair ColorFacts



Article first published January 24, 2011.

Photo Credit:asterisco; stock.xchng

Laura Jamieson

I graduated with a Bachelor of Science degree in chemistry from the University of Guelph. I recently completed a Bachelor of Education from the University of Western Ontario and am pursuing a career teaching chemistry.

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