An unequivocal answer is difficult to give.
A tattoo can greatly affect health, if, for example, it was applied in violation of the rules of asepsis and antisepsis. In such cases, the risk of contracting an infectious or viral (hepatitis C) disease is extremely high. But a similar situation is with beauty salons (manicure, pedicure, piercing, etc.).
There is no direct direct negative or positive effect on the body of a person with a tattoo.
As always, British / American scientists will help you with this answer.
A study by a team of scientists from the University of Alabama suggests that tattoos can improve immunity. This means that the body of tattooed people copes much better with infections than the body of those whose bodies do not have a single tattoo.
The conclusions of scientists were based on the results of a survey of visitors to tattoo parlors. Each of the respondents described how many tattoos he had and how long it took to apply them. In addition, the researchers took samples of saliva from each participant in order to measure the concentration of cortisol and immunoglobulin A, which are present in the lining of the respiratory and intestinal tract. Immunoglobulin A is needed to fight various infections, such as the common cold.
They found that after the first tattoo, the concentration of cortisol increased, which was the body's response to stress. The level of immunoglobulin A dropped and quite significantly. If the second and subsequent tattoos were applied to the body, then such a serious decrease in the concentration of immunoglobulin A did not occur. The authors conclude that if the first tattoo does not have the best effect on the immune system, then all subsequent ones, most likely, only strengthen it.
From their experience: a tattoo on the forearm measuring 10 cm, color. No health effects noted