Why do hippopotamus have skin that secretes oil?

Hippopotamuses have skin that secretes a natural oily substance, often referred to as "blood sweat," which serves several important functions. This secretion helps to keep their skin moisturized and protects it from sunburn, acting as a form of sunscreen in their natural habitat. Additionally, it has antimicrobial properties that help prevent infections in their thick skin, which can be prone to injury from their environment. Overall, this oily secretion is crucial for their health and survival in both aquatic and terrestrial environments.