Lip masks

A lip mask is used to soften and protect dry, chapped lips. Most work by sealing in moisture with a thick layer of waxes, butters, and oils, so lips lose less water while you sleep or go about your day. They smooth the surface; they don't change how your lips are built.

Usually yes. A lip mask is basically a heavier balm, so you can wear it in the daytime if you don't mind the texture. The catch is sun: many have no SPF, so if you're outdoors, use a lip product with SPF on top or instead. Check the label for fragrance if your lips irritate easily.

There's no studied schedule, so go by how your lips feel. Most people use a lip mask once a day at night, and add a layer during the day when lips feel tight. If lips get worse, itchy, or swollen, stop and check the ingredients, since fragrance and flavoring are common irritants.

Don't count on it. A lip mask can make lips look smoother and fuller by hydrating them, which changes how color reads, but evidence that a mask lightens pigmentation is thin. Dark lips have many causes, including genetics, sun, and irritation, so persistent or changing color is worth showing a dermatologist.

Not necessarily. A mild tingle can come from ingredients like menthol or camphor, or from exfoliating formulas, and some people like it. But burning, stinging that lingers, or swelling is a sign of irritation. Wipe it off and stop using that product.