3 free refers to nail polish that is free form certain substances that are potentially hazardous or harmful over time.

The Big 3 (toxic chemicals that is) | All Lacquered Up

Most modern nail polish is 3 free, with some going 4 or 5 free.

Things that aren't 3 free are more common in nail treatments and things like fast dry topcoats. 3 free and non 3 free sometimes don't play well together, causing more chipping or increased chance of nail staining.
Originally Posted by redcelticcurls
Thank you SO much, RCC you are a veritable font of wisdom From what you have said, I gather I am far better off not using the Seche-Vite ;p Well, that'll make it cheaper to do my manicures! lol!
Finer, mixed with coarser strands, low-porosity, wavy curly whirly hair...3A, 2C hair. Medium thickness, medium elasticity.
S-shaped hair with corkscrew ends. My hair is even more confused than me ;p
My hair officially hates protein Once a month is enough!
Currently a fan of TiGi products, (rock on, TiGi Curlesque styling creme!) but that will soon change - I am a self-avowed product junkie! Yay!
BIG fan of supersoaker method - thanks Rudeechick!