How exactly does this protect my skin from cold weather and dry air? I want to understand the mechanism.

The product works by forming a light, occlusive film on the skin's surface. This barrier is the key to its protective function. It physically shields the skin from external irritants like wind, frost, and dry indoor heating. Simultaneously, this film reduces transepidermal water loss, which is the evaporation of moisture from your skin. By slowing this process, it helps the skin retain its existing moisture for longer, preventing it from feeling tight or flaky after exposure to harsh conditions.

It's important to note that this is a different mechanism from a hydrating serum or cream that adds water to the skin. This petroleum jelly doesn't hydrate on its own; it locks in what's already there. For practical use, apply a thin layer to exposed areas like hands, elbows, or cheeks before going outside in cold or windy weather. This gives the barrier time to form. For overnight care on persistently rough patches, a slightly thicker application can help soften the area by creating a longer-lasting protective seal.