What is it? Sodium polyacrylate

Other names it goes by: Acrylic acid homopolymer, sodium salt, polyacrylic acid.

What's it used in? Moisturisers, anti-ageing treatments, sunscreens.

What does it do? It's used as a polymer to bind ingredients together.

Any controversy? The US Food and Drug Administration says it is safe to use in limited quantities in food, but some animal studies show it can affect sensory organs.