I wear mascara on my eyelash extensions and the only thing I take great pains to do is remove it carefully so there is no build-up or residue.
I am a Lash Extensions Arts Educator, a professional back bar Supplier, and a member of The Lashologists Council of America too! - There are so many innovations and forward thinking changes in the adhesives and materials we use, that the age old precautions and instructions for caring for the lash extensions are very quickly becoming outdated.
I use a foaming lash shampoo of baby shampoo, distilled water and baking soda to wash my eyes and eyelashes every night - including the first night of getting a touch-up or initial application. I do wear mascara (although not every day and NOT a waterproof formula). The foaming lash shampoo is an excellent and extremely gentle way to cleanse the eye.
The ratio to mix is: 1 part baby shampoo (or gentle cleanser), 3 parts distilled or newly opened bottled water + 1/2 teaspoon of baking soda. It rocks!
All the Best,
jp