OF THE AMERICAN COLLEGE OF TOXICOLOGY
Volume 2. Number 7, 1983
Final Report on the Safety
Assessment of Sodium Lauryl Sulfate
Lauryl Sulfate is an anionic surfactant used in cosmetics
and industrial chemicals as a cleansing agent. In absorption,
metabolism and excretion studies Sodium Lauryl Sulfate
had a degenerative effect on the cell membranes because
of its protein denaturing properties. High levels of skin
penetration may occur at even low use concentration.
Sodium Lauryl Sulfate had an LD 50 (Lethal Dose for 50% of the animals tested)
of 0.8 to 110 g/kg in rats. A formulation containing 15% caused depression,
labored breathing, diarrhea and death in 4 out of 20 animals.
In acute ocular tests, 10% Sodium Lauryl Sulfate caused corneal damage to the
rabbits’ eyes if not irrigated or irrigation was delayed. A Draize test
of a product containing 5.1% Sodium Lauryl Sulfate caused mild irritation and
products containing 21% were severely irritated with no rinse and mildly irritated
Acute animal skin irritation studies of 0.5% to 10% Sodium Lauryl Sulfate cause
slight to moderate irritation. Applications of 10% to 30% caused skin corrosion
and severe irritation. Solutions above 20% were highly irritating and dangerous.
One percent and 5% Sodium Lauryl Sulfate produced a significant number of comedones
when applied to the pinna of albino rabbits.
A chronic oral feeding study in rats of 0.25%, 0.5% and 1.0% Sodium Lauryl
Sulfate in the diet for two years produced no observable abnormalities except
for moderate to severe dermal effects. In mutagenesis studies, rats fed 1.13%
and 0.56% Sodium Lauryl Sulfate in the diet for 90 days produced no more chromosomal
aberrations or clastogenic effects than did a normal diet.
Sodium Lauryl Sulfate was tested for human skin irritation in concentrations
ranging from 0.1% to 10%. Open patches were less irritating than closed patches,
and irritation increased directly with concentration. For prolonged contact
with skin, concentration should not exceed 1%.
CHEMICAL AND PHYSICAL PROPERTIES
Sodium Lauryl Sulfate, an anionic surfactant, is prepared by the sulfation
of commercially available lauryl alcohol form coconut our, with either sulfur
trioxide or chlorosulfonic acid. The product of the reaction is then neutralized
with aqueous sodium hydroxide (lye). The abbreviated symbol for Sodium Lauryl
Sulfate is used around the world in clinical studies as a skin irritant. SLS
is the universal standard, by which a measured percentage is evaluated to promote
a given level of irritation and reaction. By this SLS standard level or irritation,
it is then possible to evaluate the healing or modifying characteristics of
any ingredient or formula used on the SLS irritated skin.
Carcinogenic nitrates can form in the manufacturing of Sodium Lauryl Sulfate
or by its inter reaction with other nitrogen bearing ingredients within a formulation
utilizing this ingredient
Tests show permanent eye damage in young animals from skin contact in non eye
areas. Studies at Georgia Medical College indicated Sodium Lauryl Sulfate kept
young eyes from developing properly by possibly denaturing the proteins and
not allowing for proper structural formation. This damage was permanent.
Other studies have indicated that Sodium Lauryl Sulfate enters and maintains
residual levels in the heart, the liver, the lungs and the brain from skin
contact. This poses question of it being a serious potential health threat
to its use in shampoos, cleansers, and tooth pastes.
Still other research has indicated SLS may be damaging to the immune system,
especially within the skin. Skin layers may separate and inflame due to its
protein denaturing properties.
A higher foaming and slightly less irritating modification of Sodium Lauryl
Sulfate can he manufactured by ethoxylation of the surfactant. The modified
compound becomes know as Sodium Lauryl Ether Sulfate. The cosmetic name is
Sodium Laureth Sulfate with an abbreviated symbol of SLES.
from the ACT report on the safety of SLS to Sodium Lauryl
personal and household products
The potential health-effects
SLS. The killer in