Whether we’re touching up our roots, getting back to our natural colour, changing up our look or going full-on unicorn, we love hair dye for the versatility it brings. But besides making it look super awesome pretty, what does hair dye actually do to our hair? And how does hair dye even work?

Watch and learn: How does hair dye work?

Hair dye works by coating or penetrating your hair to change its colour permanently, semi-permanently or temporarily.

Since hair dye was invented, it’s been blessing our hair by coating or penetrating our hair strands with various sizes of colour molecules to make us look and feel fabulous.

Dyeing your hair at home has become a common process – whether it’s to cover grey, change up your style, or restore your hair back to its original colour.

Will hair dye damage my hair?

If you want to know how hair dye works because you’re worried about it damaging your hair, you’d be right. Hair dye does damage your hair and at-home box dyes are the worst for frazzling your locks.

Unfortunately, it’s the way the hair dye alters the structure of your hair that causes damage. It can weaken your hair, making it try and prone to breaking and splitting.

Using deep conditioners for coloured hair can help to restore your hair in between colourings.

How deep the colour penetrates, and therefore how long it lasts and stays in your hair, depends on the type of hair dye it is.

From semi-permanent, permanent, temporary washes and even demi-permanent, there are a variety of hair dye types to suit every wish and whim.

But how does each one work? Let’s break it down.

How does permanent hair dye work?

permanent hair dye insta

Permanent hair colour is the strongest and most long-lasting of all hair dyes.

Permanent hair dye penetrates the cuticle of your hair to permanently change the colour of your hair pigment and structure.

Peroxide is the magic making chemical that that opens up the cuticle of the hair strand and lets the tiny colour colour molecules in. Once inside the hair cortex, they react and expand to a size that can’t be easily washed out.

Permanent hair dye can fade with time or in the sun, but it won’t wash out like other hair dyes. As your hair grows, your roots will who so you’ll need to re-dye your hair to cover root growth every six to eight weeks.

How does semi-permanent hair dye work?

semi-permanent colour insta

Semi-permanent hair dye lasts longer than temporary hair dye but not as long as permanent.

This is because this hair dye works by coating the outside of your hair strands with a mix of large and small colour molecules, rather than penetrating inside it or permanently altering it.

Semi-permanent hair dye contains no peroxide or ammonia, so while it’s not as effective at covering grey hairs as permanent colour, it’s kinder to the condition of your hair.

You won’t get roots growing out like you will with permanent dyes either and semi-permanent dyes typically wash out in 10-12 washes.

How does temporary hair dye work?

temporary hair dye insta

Temporary hair colours last until you wash them out!

These types of hair dyes work by painting or spraying colour on top of your hair strands. Temporary colour doesn’t penetrate or alter your your hair shaft in any way and are great for experimenting with crazy colours.

This means you change up your colour for a night out, a special occasion or even just for fun!

How does henna hair dye work?

henna hair dye insta

Henna is a natural, plant-based hair dye, made from the lawsonia inermis shrub.

Henna contains no nasty chemical and works by naturally sitting on the surface of the hair strand, sinking in and staining it.

Henna hair dye traditionally comes as a powder or mixed with coconut oil and is best for red or auburn hair shades as it deposits a reddish pigment.

Henna can be messy to apply, and tricky to remove. But people love it for its natural, conditioning properties. The layer of colour over the hair provides a protective coat which has shine-enhancing and hair strengthening qualities.

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