A recent medical study found an association between tattoos and malignant lymphoma, with a 21% increased risk of this type of cancer in tattooed persons. Published in the Lancet (oh, the irony!), the paper notes that tattoo ink contains known carcinogens. Nevertheless, the popularity of getting inked has skyrocketed in the past few decades.

Within living memory, the idea of having things injected into one’s body was generally viewed with aversion. The horror of intravenous drug addiction and the specter of AIDS both played a role in this. Still, there is a natural terror of having one’s skin penetrated that is – or at least was – inherent to the human psyche: consider the enduring popularity of vampire mythology as a staple of the horror genre.

Children in particular have always had a hatred of needles, and with good reason: first, it’s an obvious invasion of their physical person, and second, it hurts. Holding down a struggling child to inject them with a vaccine (often while insisting to them it’s for their own good) is a perennial litmus test for medical students as they decide upon their specialty of choice. After all, if you’re not willing to overpower young children and force needles through their skin, you’ll have a hard time making a living as a pediatrician.

In my estimation, human distaste for the hypodermic route of administration is both perfectly natural and adaptive to survival. The skin is the body’s largest and most important barrier to infection and injury, and any breach of it is potentially dangerous.