07/05/2015 09:09 BST | Updated 06/05/2016 06:59 BST

Sulphate Free Shampoo - Would You Wash Your Hair in Engine Degreaser?

You can't hit a supermarket hair-care aisle these days without bumping into yet another 'free-from' shampoo, claiming fabulously glossy hair, sans the sulphates.

When the major hair care brands (L'Oréal for example) start hiring supermodels to promote sulphate free shampoo, it must make you wonder. Is sulphate free shampoo just a clever move to tap into the latest consumer trend, or is there really cause for concern about sulphates?

As far as rigorous scientific analysis goes, no one is really sure. There simply is not enough published research on the long run effects of sulphate use on hair colour, curls and scalp health.

As we discovered during our research for our recent article 'Seven reasons to choose a sulphate free shampoo', the most informed opinions on the long term effects of sulphate use come from hairdressers.

Given how much hair they wash, cut, colour and style in their career, professional hairdressers might be infinitely better qualified than most to evaluate the long term effect of hair products on people's scalp and hair. We found a trawl of expert hair communities online quite revealing on this issue.

A number of hairdressers were quoted as saying that sulphate shampoos 'strip' hair colour, 'interfere' with curls and customers with dry scalps are 'keener than ever' to avoid them.

Other sites even point to anecdotal evidence of sulphates contributing to hair loss.

But why? What in the chemical make-up of sulphates is causing this concern about short-medium term effects on the hair and scalp?

To understand the power of sulphates, it's worth pointing out that the most common one, sodium lauryl sulfate (SLS), is not just used in shampoo and toothpaste, but also in industrial cleaning products, even engine degreaser.

That alone is not a good enough reason to avoid them (although probably enough to put some people off). But sulphates are strong detergents that bind with the dirt and natural oils in your hair and scalp. The scientific studies that have been done on sodium lauryl sulfate have identified it as an irritant in 'leave-on cosmetics' at anything more than 1%. This explains why many with dry, itchy scalps find a sulphate free shampoo less likely to exacerbate existing conditions.

SLS is still considered safe for use in rinse-off products like shampoo and shower gel. What's missing is a study on the cumulative effect of using a sulphate shampoo every day, potentially where it is left on the scalp for several minutes before being rinsed. That is a concern.

There are milder forms of SLS - sodium laurETH or myreth sulfate for example. Again there's not much research on long term use, but the production process of these modified forms (ethoxylation) is not good news for the environment.

Another reason we'd choose to opt for sulphate free is that it is generally a marker for 'kinder' shampoo.

Shampoos labelled sulphate or SLS free, generally have less harsh detergents as well as a higher level of naturally nourishing botanical ingredients that encourage scalp health, smooth the follicles and promote shine. In that respect they also provide a reasonable indicator of a more hair- and scalp-friendly shampoo.

But we feel it important to point out that not all Sulphate Free shampoos are created equal. 'Sulphate Free' may still mean harsh preservatives, fragrance and other potential irritants.

Organic certification is a really a much better gauge that a shampoo formulation is entirely 'clean'- meaning less likely to contain nasties full-stop.

We recommend looking for good ingredients like beauty super-hero coconut oil that naturally conditions the scalp and is one of the few oils that can penetrate the hair and promote healthy-looking locks.

Herbal extracts such as rosemary, nettle, horsetail and chamomile are also great for the hair, but as with all botanicals, look for the position on the ingredients list - the higher up the better as it means there's more of them.

In short - yes we absolutely agree that a sulphate-free shampoo is a good thing, but take the time to check the other ingredients and really look at what you are buying - it's a matter of assessing the ingredients left IN as well as what has been taken OUT.