Got tats? Researchers at the University of Alabama in early March of 2016 suggest that a person's immune system could be strengthened by getting multiple tattoos. To reach this conclusion, researchers measured the cortisol levels in tattoo parlor customers with a saliva sample. (Cortisol is a stress hormone that suppresses the immune response.) Tests showed that immune responses were down in those who received their first tattoos, but were higher in individuals with multiple tattoos. It can be related to being tired after your first workout in a while, compared to feeling fine after working out over a longer period of time.