While it may seem as though the first two days of skin cycling are the most important, know that those rest days are equally, if not more, critical, says Castilla. Giving your skin a chance to breathe, recoup, and become accustomed to the actives from the previous two days is essential, otherwise there’s a higher chance you’ll experience adverse effects like flakiness, irritation, soreness, and dryness. A little of the latter is normal in the beginning, but if you’re thinking about practicing slugging — another TikTok skin-care trend that involves coating your face with petroleum jelly — to offset any dryness, Castilla says to forget about it, because “it can clog your pores and lead to an acne breakout, especially on the exfoliation night.” She also warns that people prone to conditions like eczema, dermatitis, or very dry skin in general may find the regimen too irritating for them.