system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why do companies put caffeine in soaps?

Does your body absorb it somehow? Does it help as a moisturizer?
gpt
There have been a few studies, according to a "board certified dermatologist at Modern Dermatology in seattle" - “Topical caffeine is best known for its antioxidant properties. With topical antioxidants, you can decrease the harmful effects of free radicals created by environmental pollutants and UV radiation, which are what cause fine lines and wrinkles.” He goes on: “Caffeine has been shown to constrict blood vessels when applied to the skin. It is thought that caffeine may temporarily constrict these tiny blood vessels, somewhat masking the darkness under the eyes. Furthermore, caffeine-enhanced skincare products can decrease inflammation and irritation. They may reduce swelling and feel ‘soothing.’ ”