Getting one tattoo or more could boost people's immune response, leaving them better protected against colds and common infections.

This is the conclusion of a study, published in the American Journal of Human biology. Lead author Dr. Christopher Lynn, professor of anthropology at the University of Alabama, says getting a tattoo temporarily weakens the immunological system, only to make it stronger to new infections.

This research comes after Lynn experienced first-hand the physically draining sensation that came with getting a tattoo. "Tattooing doesn't just hurt you, it can exhaust you," Lynn said. "It's easier to get sick. You can catch a cold because your defences are lowered from the stress of getting a tattoo."

Saliva samples analysis

Lynn together with two scientists set about recruiting volunteers amongst prospective clients at various tattoo parlours. In total, 24 women and five men, aged between 18 and 47 agreed to take part. The participants were asked if they already had tattoos, how many, and when they had them done. Saliva samples were taken and analysed before and after the participant got a tattoo, regardless whether it was their first one or not.

The scientists measured levels of immunoglobulin A, the antibody which acts as a first line of defence in the mucous membranes, and cortisol, a stress hormone known to suppress the body's immune response.

People get stronger

The compared samples indicated levels of immunoglobulin A decreased when participants received a tattoo for the first time. At the same time, levels of cortisol increased, suppressing immune responses and confirming that getting a tattoo can cause a stressful sensation. These variations were less marked for participants who were not receiving the tattoo for the first time.

"People with more tattoo experience have a statistically smaller decrease in immunoglobulin A from before to after," Lynn explained.

High levels of immunoglobulin A also suggests the body triggers a prompt immune response when a person gets a tattoo, mobilising antibodies to prevent potential infections. Immunological agents become quicker to react to infections and colds after tackling them first time round, following previous tattoo sessions. After multiple tattoos, the body becomes progressively stronger.

The scientists believe this type of research, which mixes anthropology and biology is crucial, because it looks at practices that matter to a lot of people in a fresh way. "The trick is to find ways to study catchy concepts that are also important. Nobody had done anything like this tattooing study, looking at the potential benefits from a biological perspective" Lynn stressed.