21% of adults in the United States have at least one tattoo, according to the Centers for Disease Control (CDC) and on occasion outbreaks of nontuberculous mycobacterial (NTM) skin infections have been reported after tattooing.

In January 2012, public health officials in New York received reports of Mycobacterium chelonae skin infections in 14 New York residents who received tattoos during September–December 2011. All infections were associated with use of the same nationally distributed, pre-diluted gray ink manufactured by "company A". 

Public health investigations by CDC, state and local health departments, and the Food and Drug Administration (FDA) found NTM contamination in tattoo inks used in two of five identified clusters. All infected persons were exposed to one of four different brands of ink. NTM contamination of inks can occur during the manufacturing process as a result of using contaminated ingredients or poor manufacturing practices, or when inks are diluted with nonsterile water by tattoo artists.

Oddly, the government regulates cutting hair yet there is no FDA regulatory requirement that tattoo inks must be sterile.  This is one instance where conservatives and liberals alike would likely argue a business absolutely should have a health guideline.  Almost as many people have tattoos as smoke and smokers are micro-regulated.  

The CDC does recommend that people should be aware of the health risks associated with getting an intradermal tattoo. 

On January 4, 2012, the Monroe County (New York) Department of Public Health began an outbreak investigation after receiving a report of a person with a persistent papular rash beginning 1 week after being tattooed by an artist in October 2011; M. chelonae was isolated from a skin biopsy. Since May 2011, the artist had been using company A pre-diluted gray ink. Using a list of customers provided by the artist, a total of 19 infections were identified, including 14 confirmed with M. chelonae.

All infected persons had been tattooed with "company A" pre-diluted gray ink. The tattoo artist said he had not diluted the ink before use, and a review of his practices did not reveal other potential sources of contamination. M. chelonae was isolated from tissue specimens, and from one opened and one unopened bottle of company A pre-diluted gray ink. Pulsed-field gel electrophoresis (PFGE) patterns of 11 available patient isolates and an unopened bottle of company A pre-diluted gray ink were indistinguishable; the M. chelonae isolate from the opened ink bottle showed ≥95% genetic relatedness to the other isolates. Water and environmental samples collected at the manufacturing company and tattoo parlor were negative for M. chelonae.

The New York cluster included 14 confirmed and four probable cases, and one possible case. An investigation by Public Health – Seattle&King County, Washington, identified five confirmed and 26 possible cases. Confirmed cases also were reported from Iowa (two) and Colorado (one) (Table). Among 22 confirmed cases, 63.6% involved men, and the median age of persons in the 22 cases was 33.5 years (range: 20–48 years).

Source: CDC