Rekha Garton via Getty Images A recent study suggests that having multiple tattoos could mean your immune system has trained itself to better respond to certain stresses.

The next time Grandma criticizes your multiple tattoos, tell her they might just be a sign that you're healthy.

A new study published in the American Journal of Human Biology last week -- and getting lots of ink since then -- suggests that people with multiple tattoos have a better immune response to new tattoos than people who are getting tattooed for the first time.

According to the research, "Tattooing may stimulate the immune system in a manner similar to a vaccination to be less susceptible to future pathogenic inﬁltration." While the study has a small sample size and is not yet conclusive, it provides fascinating evidence of how well the body can be "trained" to respond to stresses over time.

For the study, researchers at the University of Alabama collected saliva samples from 29 volunteers before and after they were given tattoos. Nine of those participants were receiving tattoos for the first time. They then analyzed the participants' saliva samples for levels of immunoglobulin A, an antibody that lines portions of our gastrointestinal and respiratory systems, and cortisol, a stress hormone known to suppress immune response.

“Immunoglobulin A is a front line of defense against some of the common infections we encounter, like colds,” Christopher Lynn, an associate professor of anthropology at the University of Alabama who co-authored the study, wrote in a press release.

According to the researchers, the saliva samples from first-time tattoo recipients showed their levels of immunoglobulin A declined much more dramatically than they did for the people who already had multiple tattoos, suggesting that people with more "tattoo experience" had immune systems that were more habituated to that kind of stress.

Lynn isn't suggesting people go out and get full sleeve tattoos to ward off colds and the flu just yet. In fact, he said, a person's first tattoo can make them more, not less, susceptible to illness.

“They don’t just hurt while you get the tattoo, but they can exhaust you,” he said in the release. “It’s easier to get sick. You can catch a cold because your defenses are lowered from the stress of getting a tattoo.”

Lynn compares the body's response to getting a tattoo for the first time to an out-of-shape person exercising in the gym: Muscles are sore at first, but the pain fades with repeated workouts.

“After the stress response, your body returns to an equilibrium,” Lynn said. “However, if you continue to stress your body over and over again, instead of returning to the same set point, it adjusts its internal set points and moves higher.”

But other experts are poking holes in the findings. Dr. Sylvie Stacy, an Alabama physician who specializes in preventive medicine, points out the study used a small sample of subjects and investigated only a couple of the many substances involved in immune response in the body.

"I would not encourage anyone to get a tattoo for the sake of immune system benefit," she told HuffPost. "Getting a tattoo carries significant risks -- including infection, scarring, and potential adverse psychological effects. It’s very unlikely that these risks are outweighed by any boost in immune system response."

Lynn acknowledges that the study's findings could also mean that people who are already in good health are more likely to get multiple tattoos, because their immune systems are better at recovering from them and their past tattoo experiences have been more satisfactory.

"They probably already had good immune systems, and we think the tattoos draw attention to this," he told HuffPost. "We also think that, among those with good immune systems who are into tattooing culture and get tattoos, the quick healing and positive reaction may reinforce an interest in getting more."

Conversely, people who had a bad immune reaction to their first tattoo aren't as likely to come back for more. The study points out that historically, tattoos appeared to be a way for healthy, "attractive" people to differentiate themselves from less-healthy peers, and that could still be the case -- multiple tattoos mean you can handle the pain.

Of course, the research didn't involve people who chose not to get any tattoos at all. "We did not collect biomarkers (saliva) from non-tattooed [people] because we were comparing the pre-post tattoo session change, not absolute values related to immunity," Lynn said. "It would be difficult to come up with a scenario that is similar to tattooing to do pre-post testing of non-tattooed."

While the University of Alabama study takes a specific look at immune responses to tattoos, however, it also contributes to existing research on different techniques that could sharpen the effectiveness of vaccines, such as injecting them in a way that's similar to how tattoo artists inject ink under the skin.

"There is ... evidence suggesting that applying a vaccine with a tattoo approach -- several small punctures, not one big shot -- may increase the effectiveness," Lynn said.

The research is piquing the interest of medical experts like Dr. Amesh Adalia, a board-certified infectious disease physician at the University of Pittsburgh.

"Such a finding is provocative and future studies are required that assess other arms of the immune system, reproduce the results, and gauge the real-world effects in terms of vaccine responses as well as frequency of infections in tattoo recipients," Adalia said by email.

If anything, Lynn hopes the study reduces the stigma associated with getting inked up. "We'd like to take tattoos out of the negative subcultural niche of bikers, sailors and risky behavior," he said.