Not used at all

RENEE Madness pH stick is a stick of absolute magic when you want to keep the affairs of your lips hush hush! It is a lipstick with a bullet that appears black but transforms into a unique pink shade according to your skin's pH level. It's like wearing lipstick without letting anyone know you are wearing one! Your lips come alive as they respond to it, giving you a shade of pink that’s perfectly unique to your skin tone. Enriched with Jojoba oil, Macadamia oil, Olive oil, & Shea butter, this formula puts your lips under a spell of intense moisture & nourishment.

Looks black but gives glossy pink pay-off.
Transforms as per skin's pH level.
Heals, moisturizes, & softens lips.
Vegan & paraben free formula.

Once exposed to moisture, it turns a bright pinkish-red. So, yes, it is technically reacting to your individual skin in that your skin has a higher pH than the lipstick tube and also has water in it, but other than that, things aren't much more personalized. The only real difference lays in your skin tone