Technological changes have greatly impacted the process of tattooing as well as its rise in popularity, beginning with Thomas Edison's electrically powered stencil pen in 1875. Although the pen's "intended use was to transfer designs onto textiles by pricking holes in paper in the required pattern", Samuel O'Reilly modified the machine in 1891 and patented it as the first tattoo machine (van Dinter 2005:48).

Invention of the tattoo machine decreased much of the pain associated with getting a tattoo. Did it also decrease the tattoo's significance by making it easier, less dangerous, and more accessible? "The technique ignored the penetration of the outer skin that was essential to the operation, and pain was virtually eliminated" (Bradley 2000:148). Without the possibility of infection and great investment in pain, the tattoo might have become nothing more than a fad. Does this necessarily mean that in cultures where traditional techniques are still used, the tattoo has a deeper meaning? Even without a great investment in terms of pain, there is a monetary and time investment. For heavily tattooed persons the uncertainty of how a certain strata of society will receive them or even whether they will be barred from some kinds of work because of their tattoos are considerations. This would suggest that the difference between a person with tattoos and a tattooed person, the former being able to easily hide the fact that they are tattooed while the latter must embrace the tattoo identity wholeheartedly because they are more visibly tattooed, is reflected in the depth of meaning they ascribe to their tattoos.

Prior to the invention of the modern tattoo machine, some of the biggest health worries about tattoos had to do with the pain, swelling, and bleeding associated with traditional methods of tattooing, as well as the possibility of infection of the wound afterwards. This gave rise to a variety of prohibitions or taboos about tattooing that attempted to minimalize the possible negative effects. For instance, Maori women were prohibited from eating greasy foods after getting their lips tattooed and were told that if they attempted to look at or touch their tattoo before it had completely healed, it would disappear. The tattoo process was also fraught with a variety of rituals and prohibitions that were strictly followed to ensure that harmful side effects were as minimal as possible. The rituals and customs varied from location to location, but their ultimate purpose was to ensure that the process of tattooing did not cause any permanent damage (other than the intended skin pigmentation).

Today, pain, swelling, and bleeding are minimized through the use of the electric tattoo machine, but the possibility of infection is still a serious consideration. Tattoos have been linked to hepatitis B and C, HIV, the herpes simplex virus, tetanus, and staph and fungal infections. Hepatitis C is of greatest concern because tattoo needles do not usually carry enough blood to transmit HIV. While the other infections are not life threatening, Hepatitis C is a viral infection for which there is no cure, and it usually leads to fatal liver disease. It is "considered a major public health risk because it is a silent disease, which lies dormant for decades before it flares up" (Peck 2003:69). According to Dr. Robert Haley, chief of epidemiology at the University of Texas Southwestern Medical Center, "People who had do-it-yourself tattoos have a three times greater risk for hepatitis C than people without tattoos....People who get tattoos at commercial tattoo parlors have a nine times greater risk" (Peck 2003:69). One of the most famous cases of infection spread by tattoo needles involves actress Pamela Anderson who in 2002 accused her ex-husband drummer Tommy Lee of giving her hepatitis C via an infected tattoo needle that they shared to get each other's names tattooed on their ring fingers in lieu of wedding bands. This accusation caused a furor in the media, and new questions were raised about the safety of tattooing.

In addition to concerns about the safety of the process of tattooing, allergic reactions to the pigments and metals in certain inks, although usually minor, are another medical concern. Such reactions can cause swelling, itching, and oozing of clear liquid from the tattoo. In rare cases, a susceptible person could go into anaphylactic shock, a hypersensitive reaction that could be life threatening, although this has never been documented in the United States.

Another health concern about tattoo inks, is that in some cases the metal in the inks can interact with magnetic fields produced by MRI scanners and burn the skin or distort the image. This reaction is exceedingly rare, but it has been documented. In an article published in the American Journal of Roentgenology, Ratnapalan, et al. states that "all three reported cases...had dark black tattoos that caused a burning sensation during MRI. The ink used for black or dark brown tattooing may contain compounds of ironoxide that have ferromagnetic properties and may cause burningduring MRI, especially if the design is in loop patterns.The other pigments used for tattooing—namely carbon (black),titanium dioxide (white), copper phthalocyanine (blue, green),and indigoid (red)—did not seem to have ferromagneticeffects when tested with a magnet" (2004). Additionally, homemade tattoos have a higher likelihood of experiencing these reactions because of higher concentrations of metals in the skin. They recommend that the medical community be aware of these possible effects when dealing with patients who have dark tattoos. It is possible that this side effect will become more common as more and more people become tattooed or as already tattooed people age and begin to experience health problems that require the use of an MRI. This side effect, although not life-threatening, can be problematic, with some patients choosing to get a tattoo removed in order to permit an MRI scan (Ratnapalan, et al. 2004).

Because of the concern over the spread of disease as well as dominant views of tattooing in the U.S. as a low-class, foolish, and deviant practice, tattooing was made illegal in many states. In 1944, a tattooist by the name of Charlie Wagner was fined by New York City for failing to sterilize his needles. This is the first know legal action against a tattooist in the United States. Age restrictions had been in place prior to WWII, but following the war, "many municipal authorities began to take a closer look at tattooing, and newly tightened health and age regulations forced the closure of many shops across the country" (DeMello 2000:66). Many tattoo artists worked together with authorities to tighten regulations and discourage so called "scratchers" in order to gain some legitimacy for their profession. Today sterilization laws almost everywhere in the US require that tattoo artists sterilize all equipment and surface areas and use only disposable needles.