Yup - just like everything else in the modern world, modern tattoo ink is now loaded with poison.

If you look back at ancient tribes that had lots of tattoos in their culture (the New Zealand Māori for example), they used natural inks made of natural earth elements. Now, everything is just synthetic chemicals. 

 well that explains it. I keep watching friends do it. I live in Costa Rica and it's really common. I always found it weird how it became such a big trend