Lip balms are not designed to repair your skin. Instead, their emollient properties create a barrier between your thin, vulnerable lips and the surrounding air. Skin becomes dry when water in its upper epidermal layers evaporates; this is enhanced when the air is particularly dry as on a cold day. Since the skin on our lips is four times thinner than elsewhere and lacks protective sweat and oil glands, it is more vulnerable to moisture loss than anywhere else.
To counteract moisture evaporation, lip balms use fatty substances to form a temporary protective wall. Commonly, petroleum jelly or petrolatum is used, but beeswax and shea butter can also create a barrier which prevents water from evaporating into the surrounding dry air. However, it doesn’t take long for this barrier to break down, especially because we are constantly eating and licking our lips.
So if you really want to keep your lips silky soft, it’s best to apply lip balm after you get out of the shower to lock in extra moisture. The more protection, the better: after all, it’s not like you can become addicted.