Yes, caffeine can be absorbed through the scalp. Caffeine is a small molecule that can easily pass through the skin and into the bloodstream. In fact, studies have shown that caffeine applied to the skin is just as effective as taking it orally in terms of its effects on the body. So, if you're looking for a quick fix of energy, applying some coffee grounds or caffeine-infused shampoo to your scalp might just do the trick!