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What are Azo Dyes and are they safe?

November 11, 2014

A splash of colour can make the world of difference to a product, bringing it to life, giving it personality and style, making it appear richer, more ‘active’, natural or wholesome than just another pot of white stuff.  But this realisation brings with it a problem or two,   there are many beautiful colours used in cosmetics but most are not natural and some, like the Azo dyes require a degree in Organic chemistry to work them out.  Or do they?

Cosmetic grade Azo can be made to be soluble in oil, or water depending on what you want to do with them but before we get to that we should look a bit closer at the chemistry of the Dye.

I have put together a  list of Azo Dyes used in cosmetic manufacture and their EU regs status:

Cosmetic Azo Dyes


Azo dyes are synthetic colours that have their origins in 19th century Europe (mainly Germany but with much frantic chemistry and patent quarrels happening in parallel both in the UK and Switzerland).  These dyes are created by forming a compound which includes a nitrogen=nitrogen double bond that looks rather like this:

azo compound

With Nitrogen making up 78% of the air that we breathe it wasn’t so hard for chemists to get hold of nitrogen to play with.  What was hard is getting it to react as it naturally sits with a triple bond holding the two nitrogens together and breaking that party took a lot of energy.

Nitrogen triple bond

Chemists found that varying the R groups on the end of those N’s gives rise to a whole host of colours including those that we see above and while this has been amazing in terms of our ability to bring colour to our cosmetic world it hasn’t been without issue.   Sometimes the R group on the above is a benzene ring  -another term for these benzene containing chemicals is ‘aromatic compounds’ although this term is a little over-simplistic for die hard (no pun intended) chemist.   It has since been found that under certain conditions these Benzene containing Azo dyes can break down to release toxic aromatic amines , some of which are known carcinogens.

The fact that some azo dyes can break down and release carcinogens is a huge concern for the general public who would find it next to impossible to adequately identify potential risks and therefore seek to avoid such colourants.  This problem is made all the more scary since Azo dyes are used to colour clothing (including leather) and home furnishings amongst other things.  To make matters worse the fact that these sorts of items are manufactured and traded fluidly throughout the world can leave us open to risks as we saw here in Australia in May this year when dodgy jeans and pillow cases made the news thanks to these dyes. But we need not all become armchair investigators as governments all over the world have recognised these risks and have taken steps to minimise the risks.  The cosmetics industry also operates strict ingredient standards and like we have seen recently in the EU, when colours become problematic their usage gets restricted or even banned.  Congo Red, Sudan Black and CI Solvent Yellow are three such examples.

The break down and release of carcinogenic by-products is a major concern but it isn’t the only problem to besiege colours.  More and more research is being done into the fate of colours in UV light following on from concerns over UV induced rashes and dermatitis made worse with cosmetic use.  These free radical style reactions can affect almost any type of chemical and might result in a complete re-think of how we formulate colour cosmetics in the future.

In researching this small article I’ve discovered just how tricky it is to work through the many names of cosmetic (or indeed other colours) to find out if they are Azo dyes or not, if they are allowed in cosmetics or not, if they are likely to break down and release carcinogens or not.  If I found this process frustrating and a little long-winded I’m sure that many others would too and I’m also sure it is one reason why many people tend to avoid anything that sounds remotely synthetic.  But that need not be the case.

Next we will have a look at natural colourants that are used in cosmetics and find out how they stack up safety wise.

Until then stay bright, stay colourful.







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