What it is
Xanthan gum is a high-molecular-weight polysaccharide built from repeating units containing glucose, mannose, and glucuronic acid. Even at low levels it sharply increases the viscosity of water-based liquids, which makes it one of the most common thickeners and emulsion stabilizers in cosmetics. In sunscreens and skincare it is typically used below one percent to give body to runny formulas, suspend particles, and keep emulsions from separating. Because it can feel sticky on its own, formulators often combine it with other thickeners and rheology modifiers.
Safety & warnings
Xanthan gum is a widely used food and cosmetic ingredient with a strong tolerability record; a 2017 European Food Safety Authority review found no adverse effects even at high dietary intake and no genotoxicity concerns. On skin it is generally considered gentle, which is why it appears so commonly in leave-on products and sunscreens.
Origin & sourcing
Xanthan gum is produced by fermenting sugars such as glucose and sucrose with the bacterium Xanthomonas campestris. After fermentation the polymer is precipitated with isopropyl alcohol, then dried and milled into a water-soluble powder; a lactose-fermenting strain even allows use of whey, a cheese-making byproduct, as feedstock.
History
Xanthan gum was discovered by Allene Rosalind Jeanes and her research team at the United States Department of Agriculture, and it was commercialized by CP Kelco in the early 1960s under the trade name Kelzan. The US FDA approved it for food use in 1968, and in Europe it carries the food additive number E415.
Questions everyone asks
What does xanthan gum do in sunscreen?
It thickens the formula and stabilizes the emulsion, helping give a smooth, even texture and keeping the ingredients from separating.
Is xanthan gum natural?
It is made by fermenting sugars with bacteria, so it is naturally derived rather than petroleum-based, and it is also widely used in food as additive E415.
Is xanthan gum safe in skincare?
It has a long history of safe use in food and cosmetics and is generally well tolerated on skin at the low concentrations used in formulas.