Debunking the Myths - Sodium Lauryl Sulfate

You may have seen this ominous email floating around in your inbox somewhere:

Source: snopes.com

But take the warning with a grain of salt, as not everything in this email may be true... First of all, there is an inherent error within the email chain. It states Sodium Laureth Sulfate, and abbreviates it to SLS, while SLS is actually Sodium Lauryl Sulfate, and the abbreviation for Sodium Laureth Sulfate is SLES. The difference between the two compounds is small, with just an additional ether group in SLES. SLES tends to be a little less irritating to the skin, but other than that, the compounds are pretty much the same.
But with that little bit of snarkiness aside, let's take a closer look at the compound in question:

Sodium Lauryl Sulfate

Structure of Sodium Lauryl Sulfate

SLS is an anionic synthetic detergent, which means that it is a long carbon chain to which a sulfate group (-SO4) is attached, forming the negatively charged (anionic) part. The 12-carbon tail attached to the sulfate group gives the material its amphiphilic properties, or both water loving and water hating. The carbon end of the compound is the nonpolar, hydrophobic side, while the sulfate side is the negatively charged, polar, hydrophilic part. Amphiphilicity is required of detergents, because it needs to be water hating, so it can attach to the oils and greases to be removes, and water loving, so it can be rinsed off easily with water. This property is what makes SLS so abundant in things like shampoos and soaps etc.
However, SLS still does pose some threats. SLS has been found to have many side effects, such as:

• Eye, skin and mouth irritations
• Membrane alterations
• Harmful to the brain, heart, spleen, liver
• Chronic irritant contact dermatitis
• Harmful to normal cell function
• Corrosive to hair follicle, and can cause hair loss

With a rap sheet like this, you might wonder why SLS is used in virtually all shampoos, toothpastes, mouth washes, and more. Well while the above may be true for SLS, the concentration of SLS in these common products is too low to make a difference. Also because our skin only comes in contact with the products for a short amount of time, it doesn't affect it in any noticeably way. As long as you don't marinate your scalp in it every night, SLS will not cause any harm. 

Even if all these harmful effects were possible of SLS, nowhere on that list is "carcinogen". So how did the myth of SLS being a carcinogen come to be?

Back in the 70s, due to sketchy manufacturing processes, small amounts of nitrosamines, which are carcinogens, entered into the shampoos. Somehow, the dubious rumor began that SLS reacted with formaldehyde to make nitrosamine. However, anyone with half a brain can figure out that since first of all, nitrogen is absent in both of those compounds, there is no way to put them together to make a nitrogen containing compounds

It would take some pretty strong, black magic to make this reaction happen

SLS + Formaldehyde --> R¹N(-R²)-N=O???

Therefore, the myth that SLS is a cancer causing compound found in shampoos is FALSE. While it is true that it can be a potential skin irritant, and have dangerous side effects, we are not exposed to it for a long enough time and at a high enough concentration for it to actually affect us. So by all means, continue lathering away with your safe shampoos and soaps!

jennymu