Ammonium Lauryl Sulfate (ALS) and Sodium Lauryl Sulfate (SLS) are both commonly used surfactants in soaps and shampoos. The main difference between them is that ALS is more soluble in water.
Chemical

Both ALS and SLS contain the negatively charged lauryl sulfate ion CH3(CH2)10CH2OSO3-. However, the positively charged ions vary between compounds: ALS contains the ammonium ion NH4+, and SLS contains the sodium ion Na+.

Function ammonium lauryl sulfate

The lauryl sulfate ion makes both of these compounds a surfactant, which is short for "surfactant." As a whole, surfactants lower the surface tension of water, allowing water to penetrate into fibers, a process called "wetting."

The active ingredients in ALS and SLS are chemically identical and should therefore perform identically.

Solubility

The biggest difference between ALS and SLS is their solubility in water.

At room temperature, SLS will dissolve at a rate of 150 grams per 1 liter of water. However, nearly 500 grams of ALS will dissolve in 1 liter of water at the same temperature. In terms of the efficacy of soaps and shampoos, this difference is meaningless because soaps and shampoos are typically used in warmer water where the two compounds are more soluble. However, the relatively low solubility of SLS prevents its use in clear or colorless soaps and shampoos, as these formulations would appear cloudy at room temperature. Therefore, clear shampoos will often use ALS or other highly soluble surfactants.

toxicity

Both ALS and SLS exhibited low ingestion toxicity. Both can cause intestinal distress (nausea and diarrhea) if ingested in large amounts. The greatest risk is irritation of the nose and eyes. However, at low concentrations, such as those found in most shampoos, this risk is greatly reduced.

interesting fact

In 2000, a paper in the Journal of the American Society of Toxicology was substantially revised and posted on the Internet. This article was redacted to falsely claim that SLS causes cancer. Debunking this rumor, Snopes.com noted that the FDA allows candy manufacturers to use SLS as an ingredient in certain candies.