Lots of personal care products proudly say they're "SLS-free". What was wrong with it in the first place?
Sodium lauryl sulfate (also known as sodium dodecyl sulfate, or sodium coco-sulfate) is found in many personal care products, such as shampoo, toothpaste . It looks like this:
It has an oil-soluble "tail" (on the left) and a water-soluble "head" (with the plus/minus signs on right). This means it's very useful in making foamy bubbles and making oil and water mix together, which are its two main uses in personal care products.
If you remember from the face washing post, surfactants helps oil lift off from skin. Sodium lauryl sulfate is very good at this - a bit too good. That oil serves to keep water in your skin, and keep things out. Unfortunately SLS in larger quantities, or for longer periods of time, can strip too much, causing irritation. 5% SLS in a product is usually enough to cause irritation in most people, but many people are sensitive to far less.
However, although it's a potent irritant, there is no evidence that it causes cancer, as is sometimes claimed.
An interesting link has been found between SLS-containing toothpastes and the development of mouth ulcers or canker sores. The bottom line is, if you're prone to canker sores (sadly, I am), switching to an SLS-free toothpaste may help.
For the other toiletries, there's no need to panic and throw all the SLS-containing bottles out - if you're happy with how your SLS-containing shampoo/soap/cream, then it's probably fine. If you're experiencing itching, flaking, dryness or redness, then it might help to try out some SLS-free products.
S Marrakchi, H I Maibach. Sodium lauryl sulfate-induced irritation in the human face: regional and age-related differences. Skin Pharmacol Physiol, 2006, 19, 177.
C M Healy, M Paterson, S Joyston-Bechal, D M Williams, M H Thornhill. The effect of a sodium lauryl sulfate-free dentifrice on patients with recurrent oral ulceration. Oral Dis 1999, 5, 39.