In olden days,people used to get infections and some sort of diseases because the methods they used were not hygienic. The people didnt know about scientific method about proper hygiene and preventing infections. The same needles were used to tattoo many people and that too without any sterilizer or disinfectant being used.
A few kinds of skin infections that occur when getting tattoo designs are bacterial infections or maybe allergic reactions and sometimes a person could get some serious disease like HIV or hepatitis b.
If you want to get a tattoo done without fear of infections or diseases then you must be sure that the tattoo studio is clean. Soap and water should be available and the tattoo artist should not look like he hasn’t taken a bath for a few days.
It would also be nice if you could ask them what are the precautions they are taking to prevent infections.