Laureth-23

Laureth-23 is a nonionic surfactant made by attaching ~23 ethylene oxide units to lauryl alcohol. Lauryl alcohol is a fatty alcohol derived from coconut or palm kernel oil.

All those attached units makes it very water-loving. This is why it's used to get something oily to dissolve into something watery; it works as an emulsifier, cleansing agent, and solubilizer.

It's typically used at levels below 5% but can go up to 8.5% in hand cleansers.

Human irritation data for this ingredient looks good: a 2024 study found that Laureth-23 had the lowest irritation score of all the fatty alcohol ethoxylates tested.

Sensitization risk is also low for allergies, the CIR found:

• no primary irritation from undiluted Laureth-23 on rabbit skin
• no primary cutaneous irritation in clinical studies using it at 60%
• no evidence of sensitization in a repeated insult patch test on 168 people using a 25% solution
• no phototoxicity

The only notable finding was slight irritation of the clear membrane in the eyes of rabbits so that's worth knowing for eye-area products.

There is one caveat for this whole ingredient family: ethoxylated surfactants slowly oxidize when exposed to air, and it's the oxidation products, not the fresh material, that act as sensitizers.

A study that patch tested 528 dermatitis patients found stronger reactions to the oxidized surfactants; this is mostly a formulation and shelf life issue.

Acne

This ingredient does have a comedogenic rating of 3, but this doesn't mean a formula with this ingredient will clog pores. Human testing has proved that any finished product with this ingredient won't automatically make you break out; it really comes down to concentration, formula, and your skin.

Fungal acne

The chemistry for this ingredient is reassuring; Malassezia uses long chain fatty acids from its surroundings (C11-24) to grow, and Laureth-23 has no fatty acid for it to grab onto.

Supporting this, closely related alkyl PEG ethers like Ceteth-20 get used in Malassezia lab work as neutral carriers to disperse a separately added fatty acid (not as the food source itself).