Conventional shampoos are worrisome mainly due to two ingredients commonly found in their containers: surfactants like SLS (Sodium Lauryl Sulfate) and preservatives like parabens. A lot of ink has been spilt about the possible side-effects of these substances, some of it is just blatant fear-mongering, while the rest is based on scientific inquiry. Discerning the one from the other can be difficult in the internet age. This post aims to give you a brief overview of some of the risks, without hype or alarmism.
Give me an S, give me an L, give me another S, what do you get? Irritation
SLS made headlines in recent decades when some scientists found links between the substance and cancer. Though later investigation found those assertions to be overstated, there are other reasons to be skeptical of the chemical.
One study at the American College of Toxicology found that skin irritation can occur when concentrations exceed one percent — this is especially disquieting because concentrations of between 15 – 20 percent are not unheard of in most shampoos. The scientists also found that higher concentrations led to severe irritation and even corrosion of the skin.
Corrosion? That sounds a little drastic, doesn’t it?
To understand how they arrived at that conclusion you have to get a sense of how SLS works. In essence the surfactant operates by starting a process called protein denaturing. That is to say, one part of it connects with fats while the other attaches to water. This allows you to rinse off the greece when the water is discarded. The problem is that the process works both on the fats attached to your hair as well as to the cells on your scalp. Over time this denaturing process can cause irreversible damage.
SLS and Children
SLS has been linked to eye irritation and poor eye development in children. This happens even at low concentration levels. Even more alarming is the fact that SLS can be absorbed through the skin. Some studies have shown that this means the substance can accumulate in the one’s liver, heart and brain. On average the body seems to be able to get rid of SLS after about four to five days, but considering that many people wash their hair daily or every second day, it is possible that the surfactant can remain permanently in your body.
Putting SLS to the test
Professor Richard Guy at the University of Bath’s Department of Pharmacy and Pharmacology conducted an experiment with the BBC recently, to ascertain the toxicity of SLS. He started by putting liquid SLS, at a concentration lower than that generally found in most washing products, onto the skin of his colleague, Dr Chris van Tulleken. He did this for six hours daily, for 21 days. Guy then measured the rate at which the skin lost water before the experiment and then again at the end. Guy says that the rate of water loss is a good proxy for the skin’s ability to be an effective barrier (protector) against pathogens. In other words, if more water is lost then that is a clear indication of damage to the skin.
Results? Guy found that water loss from his colleague’s skin had gone up three fold, from 9g per square metre of skin per hour to 33 g/m²/h. He told the BBC that the change in water loss from was about halfway toward completely losing the upper most layer of the skin.
Parabens are raising eyebrows and heart rates primarily because they behave as estrogen (the female sex hormone) mimics. Some scientists have suggested that this may cause breast cells to divide more rapidly and ultimately lead to cancer, though this finding has not been conclusively confirmed in the scientific community.
The risk is however not limited to women. Several studies have found that men who have parabens absorbed through their skin due to repeated use of various cleaning products had lower sperm counts in addition to subdued testosterone levels.
It must be stated that several scientific oversight committees have evaluated parabens and have arrived at somewhat different conclusions. For instance the U.S. Food and Drug Administration, and the Cosmetic Ingredient Review (CIR) have come out as saying that parabens are safe at current exposure levels. But researchers such as the U.S. Environmental Working Group have expressed concern about the cumulative impact of using the product. That is to say, using one deodorant may not be of concern, but using shampoo, under-arm spray, and a whole host of other products may eventually take its toll on your health. More research is being done.