Ammonium lauryl sulfate (ALS) is a common ingredient in personal care and cleaning formulations, acting as a cleansing and foaming agent. It is classified as an anionic surfactant, an organic compound that reduces the surface tension of water. ALS is derived from lauryl alcohol, often sourced from natural materials like coconut or palm kernel oil, and sulfuric acid. This compound is used primarily for its ability to create a rich lather and lift dirt and oil from surfaces, including hair and skin.
Chemical Structure and Mechanism of Action
Ammonium lauryl sulfate is a salt belonging to the alkyl sulfates family. The molecule, ammonium dodecyl sulfate, is designed to interact with both oil and water simultaneously. Its structure is amphiphilic, featuring a long, nonpolar hydrocarbon chain (the hydrophobic tail) and a polar sulfate group neutralized by an ammonium ion (the hydrophilic head).
The mechanism of cleaning begins when ALS is introduced to water, where it acts by disrupting the water’s natural hydrogen bonding, thereby lowering its surface tension. This reduction allows the water to spread more easily and “wet out” surfaces, such as hair or fabric fibers. As the concentration of ALS increases, the individual molecules begin to aggregate into organized spherical structures known as micelles.
In a micelle, the hydrophobic tails cluster together in the center, sequestering themselves away from the surrounding water. The hydrophilic heads orient themselves outward, facing the aqueous solution. Oil, dirt, and grease are encapsulated within the hydrophobic core, allowing the particle to be suspended in the water and easily rinsed away. The ammonium counterion helps balance the negative charge on the sulfate group, contributing to the compound’s performance.
Primary Uses in Consumer Products
Ammonium lauryl sulfate is a common ingredient due to its foaming capacity and cost-effectiveness in formulation. It is a cleansing agent in numerous personal care items, including shampoos, body washes, and hand soaps, where consumers expect a rich, luxurious lather. The compound’s ability to emulsify oils makes it effective at removing sebum, styling product residue, and environmental contaminants from the hair and skin.
Manufacturers select ALS for its formulation benefits, as it helps create the desired thickness in liquid products. While ALS and sodium lauryl sulfate (SLS) are structurally similar, formulators may choose ALS because it can produce a higher volume of foam and is sometimes easier to thicken. Typical usage levels in personal care products like shampoo range from 8% to 15% active matter. It is also found in other applications such as bubble baths, facial cleansers, and laundry detergents.
Evaluating the Safety and Irritation Potential
Concerns regarding sulfates like Ammonium Lauryl Sulfate often center on potential irritation and misinformation. The Cosmetic Ingredient Review (CIR) Expert Panel has assessed the safety of ALS. Their findings indicate that ALS is safe for use in cosmetic products when formulated for brief, discontinuous use, such as a product that is immediately rinsed off the skin or hair.
The potential for skin and eye irritation is concentration-dependent, a characteristic common to many detergents. Studies have shown that ALS can be irritating at concentrations of 2% and greater in patch testing. However, in most finished cosmetic products, the irritant property is attenuated through balanced formulations that include conditioning ingredients. For products intended for prolonged contact with the skin, such as lotions, the concentration of ALS is limited to no more than 1% to minimize adverse effects.
A misconception is the link between ALS and cancer, but scientific evidence does not support this claim. Organizations, including the American Cancer Society and the International Agency for Research on Cancer (IARC), have not classified ALS or similar sulfates as carcinogens. The myth likely originated from misinterpretations of scientific studies or confusion with other chemicals. The consensus is that Ammonium Lauryl Sulfate, when used within established guidelines, does not pose a cancer risk.