Ammonium Lauryl Sulfate (ALS) and Sodium Lauryl Sulfate (SLS) are common primary or secondary detergents in commercial shampoo formulas. Should you be looking for one or the other in the shampoo you choose for your hair?
In terms of chemists working up a formula for a shampoo, the biggest difference between the two is how soluble they are in water. ALS is more than three times as soluble in water compared to SLS, which makes it an attractive ingredient for chemists to choose for use in clear or colourless products.
As to how they perform in your hair removing oil and dirt, they are identical. Both are recognised as being very effective detergents, particularly in lifting oily dirt.
Is either ingredient toxic? Both ALS and SLS share similar toxicity and pH profiles. So if you have an urge to drink your shampoo or rub it into your eyes, both ingredients will have the same effect. Basically, they will both taste awful, are very unlikely make you sick, and sting quite a bit if you get it in your eyes.
Does Sodium Lauryl Sulfate cause cancer? No, this is an urban myth. In 2000 a report on SLS from the Journal of the American College of Toxicology was altered heavily to falsely imply that SLS caused cancer. This bogus report has since been widely copied and circulated on the internet.
This falsified report is still frequently cited by small, independent shampoo companies trying to promote sulfate-free shampoo as an antidote to female pattern hair loss, among other health issues. To date no connection has been demonstrated between the use of sulfates in commercially available shampoos and ill health or hair loss.
Shampoos that use ALS or SLS are completely safe for normal external use and are perfectly effective to use on all hair types. Provided the shampoo is rinsed thoroughly from the hair, there is no risk of irritation to even sensitive skin.