The act of tattooing, which is described in detail below, is practiced with a bundle of needles. It enters the skin between the dermis and epidermis. Therefore the hands come into contact with the client's blood. The procedure described above must be scrupulously respected. This prevents the transmission of disease from tattoos to the client, the client's tattoos and cross-transmission of a previous client to current client. If this procedure is not followed, here is a list of viruses / bacteria that may be possible to transmit either the tattooist or the client the wearer: AIDS, hepatitis C, Staphylococcus (eg : golden) mushrooms.
This transmission is extremely rare, but it is certain that given the gravity, it is best to check that you have in front of a person carefully.
Which indicates that if the tattooist and / or the customer is carrying one of these "diseases", the transmission is close to 0 in the strict observance of these rules.