Cosmetics should not be shared, especially those intended for the mouth.

If you have to use Tooth & Nail on more than one person, first transfer all the colour you need onto a separate mixing palette for use.
Work back and forth from the mixing palette only.
NEVER double-dip into the Tooth & Nail Palette.

Use disposable applicators or carefully disinfect tools afterwards.

Spraying alcohol onto your Tooth & Nail Palette is not sufficient to stop cross-infection.