I am NOT saying that you should avoid getting tattooed or pierced by someone who lacks medical knowledge. However, you need to take this into consideration when getting medical advice if a problem arises as a result of your tattoo or piercing.
When in doubt, seek professional medical attention.
There are 2 specific examples I can give as to why you need to consider the source when seeking advice.
1. You and a friend recently got a tattoo by 2 different tattooers at 2 different shops. Both tattoos are red, swollen and sore to the touch. You got back to where your friend had theirs done and show them yours. They proceed to tell you that it's infected and the person that tattooed you sucks and gave you an infection. Your friend then shows theirs to the same person immediately after you and is told that it's just part of the normal healing process.
2. Similar to the example above, you and a friend both got piercings at different places. You both have a lump developing at the piercing site. The person looks at the piercing they didn't do and of course tells you it's infected because the person who did it is dirty and doesn't know what they are doing. Next they look at the piercing they did and tell you not to worry, it's just a keloid.
I'm sure many of you reading this have witnessed first-hand how so-called professionals will look at a nearly identical issue and criticize the one they did not do while defending the one they did. It is individuals like this, who are trying to compensate for their lack of ability, training and professionalism that are destroying the world of body art as a whole.
The type of person described above is easy to recognize. They will start to talk badly of any competitors by whom the feel threatened almost immediately if they feel there is a chance you will go, or have already gone elsewhere for your tattoo or piercing. It is a complete waste of your time and effort to call them out on these behaviors, because people that act in this manner have usually developed an over the top ego as a way to hide from their lack of abilities and knowledge.
The bottom line is this: A good tattoo or piercing is a good one, a bad one is a bad one. It doesn't matter who did it!!!!!!!