system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How exactly does the skin healing ointment heal the cracks in the skin?
gpt
Ointments can work in a variety of ways depending on the ingredients and what you are trying to heal.

The most common ingredient is one derived from a type of oil, usually petrolatum. This can vary and some are wax based such as certain lip balms but they all provide the same purpose which is serving as a moisture barrier. It keeps the crack or break in the skin wet. In the case of cracked skin this is usually enough as the cracks are typically caused by overly dry air in the winter.

The second is to provide a barrier to foreign particles. Think of it like plastic wrap for food. It can keep dirt and dust out as well as bacteria. This keeps the crack or wound from getting infected so your body doesn't have to use energy to fight a bacteria off and devote more to healing.

Lastly are the specialized things that go in there. In burn creams usually its different substances which can cool or soothe the area. In first aid ointment it can be anti-bacterial agents. In the case of cracks usually its just some vitamins or other things that may or may not actually provide any real benefit.