Although it depends on which type of mask you’re dealing with, all outcomes aren’t ideal. While it’s relatively safe to over-apply emollients and moisturizers, leaving a hydrating sheet mask on for too long (i.e., until it’s dry) can be counterproductive—it actually causes a reversal effect where the sheet reabsorbs the moisture from the skin. On the other hand, a cleansing mask or an exfoliating mask can have an even more negative effect. “A cleansing mask may have surfactants that strip oil from the skin and over-applying these can lead to irritant dermatitis, where the skin becomes red and burning,” says Dan Belkin, MD, a board-certified dermatologist in New York City. “An exfoliating mask will often use actives like glycolic acid, which can continue to get deeper and deeper as it sits on the skin, leading to a peeling response.” If you wash or peel off a mask and notice that the skin is tender, burning, and pink, it may mean you’ve left it on too long and developed an irritant reaction. “If this happens, wash your face with warm water, stop all other actives until it resolves (e.g., retinol, glycolic acid, vitamin C, etc.), use a soothing ointment like Aquaphor ($15; amazon.com) or Vaseline ($4; target.com) liberally, and avoid too much sun exposure,” suggests Dr. Belkin. “Hydrocortisone 1% ointment is available over the counter and can soothe the skin as well.” If in doubt, or if the condition is worsening despite these steps, talk to your board-certified dermatologist. According to Dr. Belkin, something like a peel-off mask usually becomes dry and inert, and probably wouldn’t harm you to leave on too long. However, “a clay mask could potentially become irritating if left on too long, a cleansing mask is likely to cause irritant contact dermatitis if left on too long, and finally, an exfoliating mask is the most likely to cause either an irritant response or an unexpected peeling reaction,” he says. Basically, if you have sensitive skin, avoid more aggressive masks, which may result in irritation.
