WASHINGTON - The Food and Drug Administration regulates everything from lipstick and nail polish to lotions and sunscreens, but it long has ignored a possible hazard that can really get under your skin - the inks and pigments used in tattoos.

Prompted by reports of skin problems, including rashes, swelling and blistering, the FDA has started taking a hard look at materials tattoo artists have injected into the skin of some 45 million Americans.

For the first time, FDA scientists have launched studies to identify the chemical composition of tattoo and permanent makeup inks, how they break down in the body, the long-term safety effects and the products that may pose the greatest risk.

If the government ultimately decides to impose restrictions, the move could shake up an industry that attracts little regulatory oversight and bring what some say is needed protection to consumers.

"There is really no regulation," said Charles Zwerling, an ophthalmologist and chairman of the American Academy of Micropigmentation, a nonprofit group that certifies permanent makeup professionals. "The FDA doesn't do anything. If you are concerned about public safety, we need rules and guidelines."

The agency said it is aware of more than 50 different pigments used in the inks, none of which have ever been approved for injection into the skin. It said some of these pigments are "industrial strength colors suitable for printers' ink or automobile paint."

Some of these inks have caused allergic reactions, including itchy and inflamed skin. In the case of a 2005 recall of 52,114 containers of pigments made by a Texas company, more than 150 cases of swelling, cracking, peeling, blistering, scarring and chronically inflamed tissue were reported to the FDA.

Tattoos, once considered the insignia of rebels, misfits and sailors, have gone mainstream.

A survey in the Journal of the American Academy of Dermatology in 2004 found 24 percent of people between the ages of 18 and 50 have a tattoo. The Pew Research Center said a 2006 survey showed 36 percent of 18- to 25-year-olds are sporting decorative body art.

Inc. Magazine, a business publication, recently estimated there are 15,000 tattoo shops nationwide - a $2.3 billion industry made up mostly of small, individually owned shops.

Due to budget constraints and many pressing public-health priorities, the FDA said it has never exercised its power under the federal cosmetic law to regulate inks or pigments used in tattoos and in the permanent makeup for eyeliner, lip liner and eyebrow color.

FDA spokeswoman Stephanie Kwisnek said reports of skin problems, the growing popularity of tattoos and "concerns raised by the scientific community" have spurred the agency to take a closer look at the issue. An FDA consumer health report released in December carried the headline, "Think Before You Ink: Are Tattoos Safe?"

The FDA said the research, which could take several years, will supplement what has been known for some time - that tattooing can lead to skin infections and diseases such as hepatitis, tetanus and even HIV due to use of equipment that is not sterile.

The American Academy of Dermatology says tattoo inks may contain industrial organic pigments, including azo and polycyclic compounds, as well as aluminum, calcium, copper, iron, phosphorous, silica, sulfur, titanium dioxide and barium. It said these substances "may be the cause of a skin reaction like a rash or be toxic."

Rudy Saltzman, owner of Carl Arendt Custom Tattoo in Watchung, N.J., said he has used the same pigments for more than two decades, and "I have not seen any bad reactions."

"I'm not a chemist, and I don't know what's in the inks and pigments," he said. "But you can have a reaction to a deodorant. There is no way of telling how a person will react to anything."

Bill Lawyer, president of Huck Spaulding Enterprises in Voorheesville, N.Y., a major supplier of tattoo inks, said, "Our colors have been around so long they have proven themselves."

Lawyer said his family owned company has its inks and pigments tested in a laboratory in Germany to "tell us what is good and what is bad." He said he does not list all ingredients on his packages, but makes safety data sheets available to customers who want them.

With the FDA taking a back seat, regulation of the industry has been left to the states, which have varying degrees of oversight focusing primarily on making sure facilities and equipment are sanitary and meet basic health codes.

Anthony Monaco, a New Jersey state health official who is the point man for tattoo and body-art regulations, said New Jersey prohibits pigments that contain talc or toxic ingredients, but it's "very difficult to enforce."

"There are no labeling requirements for these products, and you don't know what ingredients are being used," he said. "For a long time, the industry has said this was proprietary information. If federal rules would require them to list the ingredients on the label, then the consumer would know."