The next question is does SLS break hair?
Breaking hair is not quite the right term. When hair is washed even with plain water, some protein will be found in the water. This may in part come from breakage but it may also result from normal wear of hair (i.e part of the cuticle is already weak and then falls off).
How do we know that protein comes off when hair is washed?
The simplest test is to place some hair in a container of water and shake it around. After a few hours, the hair is removed and the water is tested to see how much protein came off the hair.
How much protein comes off?
Not much is the answer. One study which performed this test for 24 hours with different solutions is really useful for our purposes. (J Soc Cosmet Chem, pp163-175,1993).
Here is a table showing how much protein they detected in the study.
|Solution||Amount of protein (mg/g)|
|Sodium lauryl sulfate (SLS)||10.3|
|Ammonium lauryl sulfate (ALS)||9.4|
|Ammonium lauryl ether sulfate (ALES)||8.1|
|Sodium lauryl ether sulfate (SLES)||7.6|
|Sodium deceth 3 sulfate (SDES)||6.6|
Taking water as our baseline, we can see that not all sulfates were created equal. Highlighted in yellow, the very effective cleansers have more protein debris than water. However other sulfates have less protein compared to water (highlighted in green).
Is there evidence that using SLS causes hair breakage?
One study on SLS reported that they would predict daily shampooing (with SLS) would lead to combing difficulties within a year and split ends within 3 years due to cuticle depletion.(Colloids and Surfaces B: Biointerphases, pp 7.14, 2005)
In my opinion this is stating the obvious. Studies looking at how hair changes as it gets older have already documented that the hair cuticle is significantly depleted and completely absent around the 20 inch mark (around 3 years assuming a 6 inch per year growth rate). (J Soc Cosmet Chem, pp 155-175, 1977).
Cuticle wear is more related to hair care practices than SLS use.
To cut a long story short, any time you handle your hair, you damage it. There is no way to eliminate this but the damage sustained can be minimised by gentle handling of hair.
Note for accuracy: Using the word sulfate (sulphate) is not quite accurate. The sulfate part of sodium lauryl sulfate is actually pretty harmless. However in the curly world , the term sulfate shampoo is commonly recognized.