From our earliest years, family members and friends often tickle our feet. There are many theories about why our feet are so ticklish, but tickling remains somewhat mysterious. Scientists say there are two ways our bodies can be tickled. The first way is when someone applies repeated, deep pressure to certain parts of your body, which might make you laugh. Primates also tickle one another and laugh when tickled. Another type of tickling happens when something lightly brushes against your skin, like a blade of grass or a small insect. This type of tickling often makes people want to scratch themselves and doesn’t usually make people laugh, except when it’s done to the feet. Experts don’t know exactly why we’re ticklish, but they have theories. Some scientists think ticklishness is a protective reflex. Tickling often causes us to try to shield or move the part of the body being tickled. This reflex may have developed through evolution to protect vulnerable areas on our bodies, like our bellies, armpits, and feet. Each of these areas is vitally important if you’re being attacked. We have a lot of critical organs in the belly, our armpits house major arteries, and we need our feet to run away from danger. Another theory is that tickling developed as a way for parents to bond with their infants. One reason feet are ticklish is that they have more densely packed nerve receptors than most other places on the body. Upwards of 8,000 nerve endings can be found in your foot, making them more sensitive and ticklish. Some people don’t have ticklish feet, which in some cases may point to an underlying health condition. For example, some people with diabetes don’t have ticklish feet because the nerve receptors in their feet have been damaged and are no longer sending sensory information to the brain. Other health concerns that non-ticklish feet may be symptoms of include metabolic syndrome and certain cancers. For those with ticklish feet who laugh and enjoy the experience, there are possible health benefits. Laughter helps protect your heart by lowering stress levels that can inflame your heart muscles and blood vessels. Laughter also burns calories; for every 15 minutes you spend laughing, your body burns between 10 to 40 calories.