Is this key ingredient in colour formulas really as harmful as most people think it is? We weighed the pros and cons after talking to the pros.

Ammonia has been used since the first hair colour formulas were created more than 100 years ago. It’s one of the two key ingredients — the other being peroxide — that’s essential to achieving hair colour changes in permanent and demi-permanent formulas. Here’s the scoop on this often-controversial ingredient.

How Ammonia Hair Colour Works.

Ammonia’s role is twofold: It opens up the hair cuticle to facilitate the oxidation process that lightens the natural colour of the hair, and it helps develop the added colour. Because hair has an acidic pH by nature, ammonia also helps it become alkaline, to create a permanent change in colour, particularly when creating high lift shades. All permanent hair colour needs a chemical alkalizer, such as ammonia or MEA (monoethanolamine), to open up the cuticle so that the ingredients in the colour formula can penetrate the hair shaft and create the desired shade.

Can Ammonia Cause Allergic Reactions?

0.5-1% of the population is truly allergic to PPD or PTD, according to Jean-Sébastien Tremblay, field education capability master and master colourist for Wella Professionals. Allergic reactions to hair colour are only triggered by PPD or PTD, the dye molecule that has been used in colour formulas since they were first developed in the 1800s. “It’s [nearly] impossible for ammonia to trigger any allergic reaction. In fact, ammonia is naturally produced in the human body. When clients complain about having a reaction to ammonia, it’s usually because they are sensitive to the smell, or added fragrances in the hair colour or have an itchy scalp because of the chemical reactions taking place during the colouring process,” says Tremblay.

Ammonia VS. MEA.

“Ammonia is a gas that easily penetrates the hair shaft to create the chemical reaction. But once that’s done it just evaporates without leaving any residue,” explains Christine Longo, professional development consultant for L’Oréal Professionnel, who oversees all product testing for colour in Canada. “But MEA is a liquid that has a bigger molecule. It opens the cuticle less, so you have to compensate by adding a larger quantity of product,“ says Tremblay. “Since MEA is a liquid, it has to be rinsed out with great care or it will continue oxidizing even after the client has walked out of the salon and cause premature colour fading.”

One solution brands that have implemented is to offer ancillary products like shampoos with added ingredients to mitigate the damage that can be caused by MEA.

Which Should I Choose?

It all depends on what you want to achieve. While Longo concurs with Tremblay in that high amounts of ammonia or MEA aren’t a good thing, knowing your clients will help you choose the best option that will keep their hair silky soft and beautiful.

For high lift shaded hair, ammonia-based formulas are your best bet. “It’s always better to chose ammonia for permanent colour rather than MEA in larger quantities,” suggests Tremblay.

For over processed hair: Neither one will create a beautiful shade. In that case, your best option is semi-permanent colour.