system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: How does our body absorb creams? Which parts of our skin do they go to?

Or oils or things like cocoa butter. I put coconut oil on my face every night but I just realised that  am not sure how or why it even works.
gpt
Hey there, pharmacist here. The most general way to understand the skin, drug absorption, lotions, and so forth is to think about how oil and water don't (easily) mix. To cross the skin barrier from outside of your skin to the inside, generally any molecule has to cross an outer lipophilic layer (which likes fat), then through a hydrophilic layer (which likes water), and then through an inner lipophilic layer. Some transdermal (across the skin) delivery systems can even increase the permeability of the skin, making it easier for molecules to get across. To address your initial question with creams and lotions, remember oil and water. The goal is to increase hydration or rather, to avoid moisture loss. So lotions on a basic level restore water. And if you put something occlusive (a lipophilic barrier like a layer of Vaseline, creams which have oils and fats in them to do the same, a bandage, etc.), you basically trap water in your skin. This is why lotions and creams work better if you put them on when your skin is still damp from a shower or bath - you trap more moisture. Hope this helps!