-
- You've seen it on
practically every detergent and shampoo
label you've ever read --sodium
lauryl sulfate (SLS) or its compatriot,
sodium laureth sulfate (SLES),
although the substance hides under a hundred
aliases. You may have
heard that SLS causes cancer, an idea which experts
pooh-pooh. If you
are confused about the safety of this common chemical
whose production
exceeds 1 million pounds in the US alone, no one would
blame
you.
-
- Sodium lauryl sulfate is a sudsing agent synthesized
from
coconut oil that makes household detergents, shampoos, and toothpastes
foam up and clean more effectively. It is inexpensive and combining it
with salt thickens it, making it a very available and useful product for
manufacturers.
-
- There is disagreement among experts as to the toxicity
of SLS.
Many experts have come out in support of SLS, stating that there
is no
evidence of danger from its use in shampoos, toothpastes, and detergents.
Health Canada and the Cosmetic Ingredient Review Expert Panel considers
SLS safe for cosmetic use.
-
- Nonetheless, the Environmental Defense Fund (Scorecard)
disagrees, listing sodium lauryl sulfate as a suspected gastrointestinal
and liver toxicant. The Safe Shoppers Bible describes SLS as an aggressive
cleaning agent and notes that although SLES is milder in action, SLES can
contain a contaminant, 1,4-dioxane, which is carcinogenic.
-
- Other sources suggest
that the presence of SLS may allow
other chemicals in a product to be
absorbed more readily. Because of its
use as a surfactant to increase
the performance of other ingredients in
cleaning products, it only
makes sense that SLS would enhance the absorption
of other chemicals.
And in fact, a search of the medical literature turns
up a study
(Baynes & Riviere, 1998) that showed SLS enhanced the absorption
of
carbaryl (Sevin) into skin. Another study (Baynes, et al. 1996) shows
SLS enhancing absorption of benzidine, a bladder carcinogen, and a third
study (Qiao, et al. 1996) demonstrates the potential of SLS in combination
with other chemicals to increase the absorption of parathion, a highly
toxic pesticide.
-
- The search did not turn up any studies that directly
implicated
SLS as a carcinogen in itself. I must note here that the way
we usually
contact chemicals like SLS is in combination with other chemicals,
although research studies rarely look at anything more than a single
chemical
at a time.
-
- But the most direct danger from SLS seems to be its
potential
as a skin, corneal, and mucosal irritant, and as an allergen.
Some dentists,
substantiated by research, warn that some people can
develop canker sores
of the mouth as a result of sensitivity to SLS.
Some may react dermatologically
to the use of shampoos with SLS and
those who are sensitive to coconut
oil may be especially
reactive.
-
- Researchers have also demonstrated that SLS can actually
increase the response to other allergens. There are, additionally, several
studies which report corneal damage and thickening after contact with low
levels of SLS. Individual reactions to the substance vary greatly,
however,
so some people may be much more sensitive than others.
-
- The bottom line,
then, is this: There are numerous chemicals
in cosmetics and cleaning
products that are more likely to be harmful to
your health than SLS;
for instance, nitrosamines and ingredients that break
down to form
formaldehyde and other carcinogens. However, less harmful
chemicals
like SLS may interact with them to increase the likelihood that
these
more toxic substances enter your body.
-
- If you are concerned about SLS
or SLES, or if you are
sensitive to the substance, read labels
carefully, know the synonyms of
these chemicals (see below) and buy
detergents, shampoos, and cleaning
products that dont contain them.
Also, you can switch to a SLS-free toothpaste
like Rembrandt Natural or
just use baking soda to brush your teeth. Most
toothpastes formulated
for young children are SLS-free. And keep shampoos
containing SLS and
SLES out of your and your childrens eyes.
-
- Go to http://www.chemfinder.com
to find
a list of over 100 synonyms for SLS, including dodecyl sodium sulfate,
SDS, hydrogen sulfate, sodium salt, aquarex methyl, avirol 101, carsonol
sls, conco sulfate wa, detergent 66, Dreft, dupanal, duponol, empicol,
emersal, finasol, gardinol, hexamol, irium, maprofix, sipon, sulfopon wa
1, sodium dodecanesulfate.
-
-
- References:
-
- Baynes RE; Riviere
JE. 1998. Influence of inert ingredients
in pesticide formulations on
dermal absorption of carbaryl. Am J Vet Res
59(2):168-75.
-
- Baynes RE; Brownie C;
Freeman H; Riviere JE. In vitro
percutaneous absorption of benzidine in
complex mechanistically defined
chemical mixtures. Toxicol Appl
Pharmacol, 141(2):497-506.
-
- Qiao GL; Brooks JD; Baynes RE; Monteiro-Riviere NA;
Williams
PL; Riviere JE. 1996. The use of mechanistically defined
chemical mixtures
(MDCM) to assess component effects on the
percutaneous absorption and cutaneous
disposition of topically exposed
chemicals. I. Studies with parathion mixtures
in isolated perfused
porcine skin. Toxicol Appl Pharmacol 141(2):473-86.
-
- Dr. Potter, along with Erin E.
Milam, is co-author of
Healthy Baby/Toxic World: Practical Ways to
Protect Your Baby During Pregnancy
and Infancy, 1999.
-
- Post your comments
and questions at the AltMed Message
Center. Copyright 1999 Melody
Milam Potter, PhD (AltM DrMeL)
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