How often should I use this mask and how does it fit with other exfoliating products like acids or retinol?

This mask is designed as an occasional intensive step, not a daily or even weekly staple; once every one to two weeks is a sensible frequency for most skin types. Because it delivers both mechanical exfoliation (the peel-off film) and chemical exfoliation (lactic acid from yogurt powder), layering it with other active exfoliants — such as glycolic, salicylic, or mandelic acid serums, or retinoid/retinol products — on the same day or even consecutive days can overload the skin, leading to redness, peeling, sensitivity, and a compromised barrier. If you use leave-on acids or retinoids in your routine, schedule the mask on a "rest" night when you skip those actives, and allow at least one full day before and after before resuming them. After the mask, focus on hydration and barrier support: a simple routine with a gentle cleanser, a soothing moisturiser containing ceramides or panthenol, and sunscreen the next morning (lactic acid and vitamin A derivatives can increase photosensitivity). If you're new to either the mask or actives, introduce them separately and monitor how your skin responds before combining.