Sodium Laurel Sulphate
Sodium lauryl sulphate (SLS) is an anionic surfactant (detergent) which is included as a foaming agent (to clean and make bubbles) in a huge variety of commonly used products. These include shampoos, soaps, face and body washes, toothpaste, washing up & laundry detergents and also industrial cleansing chemicals such as engine degreasers. There are many derivatives of SLS that can be found in commercial preparations, including sodium laureth sulphate, sodium laureth-3 sulphate, and DEA or TEA sodium lauryl sulphate. Although these derivatives may vary slightly in mildness, the general action and effects are essentially similar.
Growing Concern
Recently, there has been growing concern about the widespread use of these detergents and their safety has been called into question. In this report, we will review the scientific literature available and show why it may be wise to attempt to minimise your exposure to this family of foaming agents.
A major concern about SLS is the effect that it has when used in combination with other ingredients commonly found in personal care products. SLS has the potential to react with other ingredients (e.g. 2-bromo-2-nitropropane-1,3-diol, DEA, MEA, TEA) to form nitrosating agents, which in turn can form nitrosamines, which are known to be carcinogenic.
Similar names, different effects
There are several other surfactants with similar names to SLS – in particular ammonium lauryl sulphate and ammonium laureth sulphate. Although these sound very similar their molecular structure is significantly different and they do not have the same potential to irritate the skin. Also, because their molecules are larger than those of SLS, they are not able to pass through the skin and therefore cannot be absorbed into the body in the same way. Because of these differences, ammonium lauryl and laureth sulphates are considered to be milder and safer alternatives to SLS.
Effects of SLS on the Skin
SLS is commonly used in research laboratories as the standard ingredient (upon which all other substances are compared to) for irritating the skin.
A solution of just 2% SLS can increase skin thickness, cause irritation, inflammation (1) and increase other forms of immune activity in the skin (2). Some shampoos can contain more than 50% SLS.
SLS can cause an increase in enzyme levels in the skin, leading to redness and swelling (3). It can also lead to dryness, roughness and even flaking of the skin.
Effects of SLS in the Mouth
SLS can damage the delicate mucosal membranes in the mouth, causing the separation of epithelial layers from the mucosa (4).
Burning and severe itching of the oral mucosa following the application of SLS containing toothpaste has been reported (4).
The tissue damage caused by SLS increases with increasing concentration of SLS (4).
Switching from a toothpaste containing SLS to one without, can lead to a statistically significant decrease in the occurrence of mouth ulcers in those with recurrent aphthous ulcers (5, 6).
Effects of SLS on the Eyes
SLS can penetrate the cornea of the eye (even if absorbed through the skin), accumulate readily and is released slowly. These effects are greater in younger individuals (7). A single drop of SLS can remain in the body for 5 days, so if you wash a child’s hair more than once a week with a SLS containing shampoo, there will be constant levels of SLS present.
A solution of 1.3% SLS can reduce the rate of healing in the eye (8).
Variations in response to SLS
There is substantial inter-individual variability in the response to SLS – not everybody will be affected to the same extent (9).
Younger individuals are more susceptible to the effects of SLS (10, 11).
The effects of SLS become more harsh with increasing temperature (12). This is important to note, as most people prefer to wash in warm water.
References
1. ANDERSON C, SUNDBERG K, GROTH O. Animal model for assessment of skin irritancy. Contact Dermatitis 1986 Sept: 15 (3): 143-51.
2. LINDBERG M, FARM G, SCHEYNIUS A. Differential effects of sodium lauryl sulphate and non-ionic acid on the expression of CD1a and ICAM-1 in human epidermis. Acta Derm Venereol 1991: 71 (5): 384-8.
3. GIBSON WT, TEALL MR. Interactions of C12 surfactants with the skin: Changes in enzymes and visible and histological features of rat skin treated with sodium lauryl sulphate. Food Chem Toxicol 1983 Oct: 21 (5): 587-94.
4. HERLOFSON BB, BARKVOLL P. Oral desquamation caused by two toothpaste detergents in an experimental model. Eur J Oral Sci 1996: 104:21-26.
5. HERLOFSON BB, BARKVOLL P. Sodium lauryl sulphate and recurrent aphthous ulcers. preliminary study. Acta Odontol Scand 1994 Oct: 52(5):257-9.
6. CHAHINE L, SEMPSON N, WAGONER C. The effect of sodium lauryl sulphate on recurrent aphthous ulcers: A clinical study. Compend Contin Educ Dent 1997: 18 (12): 1238-40.
7. CLAYTON RM, GREEN K, WILSON M, ZEHIR A, JACK J, SEARLE L. The penetration of detergents into adult and infant eyes: Possible hazards of additives to ophthalmic preparations. Food Chem Toxicol 1985 Feb: 23 (2): 239-46.
8. GREEN K, JOHNSON RE, CHAPMAN JM, NELSON E, CHEEKS L. Preservative effects on the healing rate of rabbit corneal epithelium. Lens Eye Toxic Res 1989: 6 (1-2): 7-41.
9. BASKETTER DA, GRIFFITHS HA, WANG XM, WILHELM KP, MCFADDEN J. Individual, ethnic and seasonal variability in irritant susceptibility of skin: The implication for a predictive human patch test. Contact Dermatitis 1996: 35 (4): 208-13.
10. HERLOFSON BB, BARKVOLL P. Oral mucosal desquamation of pre- and post-menopausal women. A comparison of response to sodium lauryl sulphate in toothpastes. J Clin Periodontol 1996 Jun: 23 (6): 567-71.
11. SCHWINDT DA, WILHELM KP, MILLER DL, MAILBACH HI. Cumulative irritation in older and younger skin: A comparison. Acta Derm Venereol 1998: 78 (4): 279-83.
12. GOFFIN V, LETAWE C, PIERARD GE. Temperature-dependant effect of skin-cleaning products on human stratum corneum. J Toxicol 1996: 15 (2): 125-30.
http://www.greenpeople.co.uk/Organics_Features_SLS.htm
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Chemistry of shampoos
People expect a lot from shampoos. Unfortunately, it is not easy to tell a good shampoo from a poor one. Cost, fragrance, and lots of foam is what most people look for in shampoo products. Lather and foam is of little importance , but they often get the most attention.
Foaming occurs when surfactant molecules gather around air instead of oil. The result is millions of tiny bubbles. Obviously, the air bubbles are using the surfactants that should be removing dirt and oil. We have all seen shampoo advertisements showing happy, beautiful people taking showers with their heads heaped high with mounds of lather. These images have taught the public to associate lather with cleansing ability.
The truth is, lots of foamy lather only means too much shampoo was used. Excess foam equals waste. Sebum and other oils quickly destroy foam. Ideally, the head should have just enough lather to lubricate the scalp and hair. This will help your fingers massage the shampoo more effectively into the hair.
Fragrances and foaming qualities are not good ways to evaluate shampoos. Examine the hair's condition after several uses. Is it flyaway, is it hard to comb, does it seem limp, do colors fade, is the hair dry or the scalp itchy?
Carefully choose the shampoo to use and recommend. The quality of your services and the success of your repeat business may depend on the decision of product choice
The major types of surfactants are:
Anionic (an-eye-ON-ick)
Cationic (kat-eye-ON-ick)
Nonionic (non-eye-ON-ick)
Amphoteric (am-fo-TERR-ick)
Identification and names are important in all professions but for chemists, they are especially useful. Chemists try to choose names that provide information about the chemical. For example, anionic and cationic surfactants both end with "ionic" for a reason. These surfactants are a special type of chemical called an ion (EYE-on). Salt bonds are important type of chemical bonds in the hair. Salt bonds give hair many important properties and affect most chemical treatments. Although the term salt bond is used frequently in cosmetology, it is incorrect. These chemical bonds are actually called ionic bonds, and they occur between ions. Ions and ionic bonds are really quite simple to understand. Ions are molecules that have small electrical charges. These charges are positive or negative. They repel or attract each other. Opposite charges attract and similar charges repel.
Table salt, sodium chloride, is an excellent example. Sodium forms positive ions and chlorine makes negative ions. The opposite charges attract each other and make table salt. These charges are identical to those found in batteries or static electricity, but on a much smaller scale. Individual ionic bonds are very weak, but millions of them in combination are quite strong. Surfactants with a negative charge are called anionic (an-eye-ON-ick). A surfactant with a positive charge is cationic.
Anionic Surfactants (Negatively charged ion) Anionic surfactants are the most widely used detergents in the cosmetology profession. They are inexpensive, simple to prepare, and excellent cleaners. They also rinse easily from the hair. A major disadvantage is that they can be harsh and irritating to the scalp. Frequently, other surfactants and ingredients are added to reduce skin irritation.
Cationic Surfactants (Positively charged ion) Cationic surfactants are rarely used in high concentrations in the cosmetology profession. Many types are dangerous to the eyes but are safe and useful in low amounts. Until recently, their positive charges prevented them from being mixed with negatively charged anionic surfactants. Newer types, however, eliminate this incompatibility.
After all that's been said above, here's what the experts and real researchers are saying:
http://www.ctfa.org/Template.cfm?Section=Internet_Rumors&Template=/ContentManagement/ContentDisplay.cfm&ContentID=867#CTFA
CTFA Response Statement: Bogus Internet Report on Sodium Lauryl Sulfate (SLS)
October 13, 2000
There is a bogus report on the Internet purporting to be from the Journal of the American College of Toxicology (JACT). It is completely misleading and inaccurate. The original report from the Journal of the American College of Toxicology has been altered to create an inaccurate document. The erroneous report had been published at www.wwns.com/sanders/gh/lauryl.htm (no longer available).
The genuine report on SLS can be found in printed form in the JACT, Vol. 2 Number 7, 1983. The website of the American College of Toxicology, publishers of the JACT, is www.actox.org. It does NOT contain full texts of its reports.
This is an example of how information found on the Internet must be checked before using.
CTFA Response Statement:
Internet-Spread Rumors About Sodium Lauryl Sulfate (SLS) and Sodium Laureth Sulfate (SLES) Are False and Unsubstantiated
July 12, 2000
It has come to our attention that an e-mail is currently circulating on the Internet which falsely states that Sodium Lauryl Sulfate (SLS) and Sodium Laureth Sulfate (SLES), ingredients used primarily in some cosmetic “rinse off” products, are unsafe. The story relayed via e-mail is an unsubstantiated story. It is typical of Internet rumors notorious for inaccurate and false information.
There is no evidence of harm from the use of either SLS or SLES as used in cosmetic products. Both ingredients were reviewed in 1983 by the Cosmetic Ingredient Review (CIR) Expert Panel and found to be safe. Complete reports on both ingredients are available from CIR.
The Canadian Health Protection Branch (part of the Canadian government) has branded SLS e-mail stories as a hoax. On its web site (www.hc-sc.gc.ca/ehp/ehd/psb/cosmetics/sls.htm), Health Canada goes on to say “Health Canada considers SLS safe for use in cosmetics. Therefore, you can continue to use cosmetics containing SLS without worry.”
(CIR was established in 1976 by CTFA. CIR is a unique endeavor to assess the safety of ingredients used in cosmetics in an unbiased, expert manner. Its findings have established a public recorded of the safety of cosmetic ingredients. The heart of the CIR program is the Independent Expert panel consisting of world-renowned physicians and scientists. Expert Panel members must be free of any conflicts of inters, and must meet the same conflict of interest requirements as outside experts to the Food and Drug Administration (FDA).
In addition to the seven Expert Panel voting members, FDA and the Consumer Federation of American, and CTFA provide liaison members to the panel. Although funded by CTFA, CIR and the review process are distinctly separate and independent from CTFA and the cosmetic industry. CIR is located at 1101 17th Street NW, Suite 310, Washington, DC 20036, www.cir-safety.org.
American Cancer Society Response
[From: www.cancer.org]
Debunking the Myth
ACS NewsToday -- Radical chain e-mails have been flying through cyberspace stating Sodium Lauryl Sulfate or SLS, a common ingredient in many health and beauty aids, is known to cause cancer. This is not true, according to researchers.
The following are excerpt from many of the e-mails and facts that debunk this myth.
E-mail: "Sodium Laryl Sulfate or SLS is commonly found in most shampoos and toothpastes."
Fact: SLS is found in many shampoos, bath products and according to a study published in May 1997 in Journal of Clinical Periodontology, SLS is used in toothpastes and mouth rinses as an emulsifying and surface cleansing agent.
E-mail: "Sodium Laureth Sulfate (SLES) is proven to cause cancer in the long run."
Fact: This chemical and its other compounds are known irritants, not known carcinogens.
E-mail: "Check the ingredients in your shampoo and see if the have the substance by the name of Sodium Laureth Sulfate or simply SLS."
Fact: The correct abbreviation for Sodium Laureth Sulfate is "SLES." Another compound, Sodium Lauryl Sulfate, is abbreviated "SLS." The two substances have the same general formula but differ in chemical properties.
E-mail: "The fact is SLS is used to scrub garage floors."
Fact: SLS is a powerful surfactant (wetting agent) and detergent. It has industrial uses because it is a detergent which exerts emulsifying action, thereby removing oil and soil.
E-mail: "I called the company and told them their product contains a substance that will cause people to have cancer, and they say they know it but there is nothing they can do about it. They need that product to produce foam."
Fact: No manufacturer would freely admit it knowingly uses a carcinogen in its products "because we need that substance to produce foam".
E-mail: "Research has shown that in the 1980's, the chance of getting cancer is one out of 8000 and now in the 1990's, the chances of getting cancer is one in three."
Fact: According to the ACS's Cancer Facts and Figures, 1998, the occurrence of cancer increases as individuals age, and most cases affect adults middle-aged and older. Lifetime risk refers to the probability that an individual, over the course of their lifetime, will develop cancer or die from it. Currently in the US, men have a one in two lifetime risk of developing cancer, and for women the risk is one in three. During the early 1980's, the lifetime cancer risk for both men and women was one in three. This means men are slightly more at risk for cancer now, than they were then.
E-mail: "I hope we can stop giving ourselves the cancer virus."
Fact: Cancer is not a virus. There are some viruses that increase a person's risk of getting cancer, but cancer itself is not viral and not contagious. Cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells.
There is no way of knowing where this Internet information comes from. However, there are a variety of websites offering health and beauty products that are SLS-free. According to David Emery and his Urban Legends website, "Interestingly, all these Websites are maintained by 'independent distributors' for various multi-level marketing companies hawking natural personal care products. As a matter of fact, the majority of URLs returned in a standard Web search on the keywords 'sodium laureth sulfate' all point to versions of the same propaganda."
It is best to be cautious when obtaining information, especially health-related information, from the Web. Check to see who owns the site, make sure reliable sources are used and if ever in doubt, check it out.
©© 2000, ACS News Today. The American Cancer Society. All rights reserved.
