When flies land on humans, they are usually looking for a food source, as they are scavengers. Flies have a very soft, fleshy, spongelike mouth, and when they land on humans and touch the skin, they wont bite, but they will suck up secretions on the skin, such as sweat, proteins, carbohydrates, salts, sugars, and other chemicals, as well as pieces of dead skin that keep flaking off. Flies have adhesive pads on their feet called pulvilli that consist of tiny hairs that have spatula-like tips. These hairs produce a glue-like substance that helps the fly stick to surfaces. When a fly lands on a person, it is "sopping" up the moisture from the skin with its sponging mouthparts, and it is constantly dabbing the skin to gather as much moisture as possible. Flies cannot digest solid materials, so they ingest the moisture from the skin and dead skin cells. Flies do not vomit when they land on humans, but they may have been on something decaying before, which could transfer microbes that can cause diseases like cholera and typhoid.