Why Hugging Is Good For You
When you hug someone, you are offering a form of social support and receiving some in return, and this serves as protection against stress and sickness, according to a recent study. People who reported higher numbers of hugs showed less of a risk of getting sick with a common cold virus. The apparent protective effects of hugs may be attributable to the physical contact itself or to hugging being a behavioral indicator of support and intimacy.
An earlier study, published in 2003, came to a similar conclusion: 

Hugs and hand-holding in couples increased their levels of oxytocin, known as the “love hormone,” which facilitates bonding. Hugs also reduced the harmful effects of stress, and a bit of cuddling or physical contact before a rough day could carry over and protect you throughout the day.
Hugs make cortisol, the stress hormone, drop; and increase the “feel good” hormones, dopamine and serotonin. The same study found, interestingly, that people who lacked in physical contact with other human beings had higher blood pressure and heart rate than people who experienced touch often.