More than one in five Americans sports at least one tattoo, but a report from the federal Centers for Disease Control and Prevention highlights a surprising new risk — from the ink itself.

There have been 22 recent cases — and more than 30 suspected cases — of tattoo-associated skin infections caused by a type of bacterium commonly found in tap water. The infections occurred in four states — Colorado, Iowa, New York, and Washington — all associated with inks that were either diluted with unsterilized water by the ink manufacturer or by the tatoo artist before applying. Anyone considering a tattoo should take precautions, said Ruth Jones, who inspects and licenses tattoo facilities for the Quincy Health Department.

1. Use tattoo parlors registered by a local board of health. “Every establishment must be licensed by a city or town, usually the health department, since there’s not a state license,” Jones said. You should see a copy of the facility license and practitioner’s license hanging on the wall.

2. Watch to make sure the tattoo artist follows appropriate hygienic practices. The practitioner should be wearing gloves and should sterilize all equipment in an autoclave. “Watch the set up,” Jones advised. “Make sure the artist opens sterile packets to remove the needles.”

3. Understand that tattoos aren’t risk-free. Problems in licensed facilities are rare, said Jones, but there’s no way to protect completely against infections from the ink or a needle piercing the skin.