The findings highlight the need for tighter manufacturing regulations around tattoo inks.

Tattoos are all about self-expression, rebellion, reminders of family and traditions, and even drunken impulsiveness. Regardless of the reason, everyone who gets a tattoo expects that the ink that's used is safe.

A study by researchers from Binghamton University (Bing U), New York, has found that that might not be the case. Of the 54 tattoo inks they analyzed, from big-name US brands to smaller manufacturers, 90% had major labeling discrepancies, specifically unlisted additives and pigments.

Here's what the researchers found:

Polyethylene glycol (PEG) was the most common unlisted additive. While it's regularly used to treat constipation, prolonged exposure to PEG can cause harmful effects, including kidney or heart failure.

The second most common was propylene glycol, associated with skin irritation and allergic reactions.

Butylated hydroxytoluene (BHT), a food preservative that can disrupt the endocrine system, impacting testosterone levels and affecting sperm quality. In addition, it may cause liver enlargement, kidney dysfunction, and lung inflammation.

Hexamethylenetetramine, an antibiotic commonly used to treat urinary tract infections.

2-phenoxyethanol, an antimicrobial agent. Though rare, there have been cases of contact dermatitis and hives following exposure to this substance. The US FDA has warned against nervous system problems and diarrhea with nursing infants exposed to 2-phenoxyethanol by their mothers.

1-butanol. An alcohol commonly used as a solvent and fuel and reported to irritate eyes, lungs, and skin following repeated or prolonged exposure.