All of the Laureth ingredients are produced by reacting Ethylene Oxide with Lauryl Alcohol and the number associated with the Laureth – refers to the average number of repeating Ethylene Oxide units in the molecule. According to research, as the numerical value of Laureths increases, the viscosity of the ingredient increases until they become white, waxy solids.

For example, Laureth-7 is low on the Laureth scale, which reaches Laureth-40. Therefore, Laureth-7 has a low-viscosity. However, there is some research which shows that the lower the numerical value of the Laureth, the higher the risk of irritation.

Safety Measures/Side Effects:

The CIR expert panel has conducted research on two (Laureth-4 and Laureth-23) of the many Laureths and made an inclusive approval of all Laureths for the use in cosmetics. However, small amounts of 1,4-dioxane, a by-product of ethoxylation, may be found in the Laureth ingredients, and the potential presence of it can be controlled through purification steps to remove it before blending Laureth- into cosmetic formulations (Source).

Sources

https://www.truthinaging.com/ingredients/laureth-7