With a boom in face masks in the last few seasons, that old-time ritual of putting on a face mask in the privacy of one’s home is seriously passé. “Masking” is well out in the open.

In fact, there is even a beauty phenomenon called mask bingeing. “That’s when people put on several different masks in a row to treat whatever they want,” said Lev Glazman, a founder of the Fresh skin-care line.

Mr. Glazman credits millennials on Instagram for the proliferation of face mask products. “Millennials are triggering something in beauty, and then the other groups are looking and maybe following,” he said, adding that he has learned a lot from his daughters, ages 18 and 22.