Understanding the permanency of tattoos
Origins of Tattoos and Their Pigments
Tattoos are a form of art that has existed for thousands of years. It is a form of body modification where a design is made by inserting ink, dyes, and pigments into the skin to change the pigment. The oldest tattoos in the world currently known were on two mummies from Egypt, which are dated back to around 3,000 B.C. Centuries ago, different ingredients were used to make tattoos compared to what is available today. Various color combinations were discovered from natural products like copper, ashes, graphite, tree bark, and woad. For example, carbon and iron oxide were used to produce a black-colored ink. Cinnabar, which is a mercury sulfide (HgS) compound, was utilized to create red hues. Cadmium (Cd) complexes would result in various shades of red, orange, and yellow.
Today, the quality of our inks has significantly improved, and there are endless available color options. Throughout the last 25 years, ink manufacturers have diverged from the primarily mineral-based pigments to more organic ones. About 80% of colorants used today are carbon-based. So many different options exist today that if you have two different tattoos created by different tattoo artists, there is a chance that the ink from one location can be made up of materials completely distinct than that from the other tattoo. Regardless of the chemical make-up of the ink, the process of getting a tattoo made is very simple. A solid pigment creates the color and is then suspended in a liquid carrier. This liquid carrier can include water, glycerine, witch hazel, propylene, and ethanol (pure or distilled ethanol). The liquid carrier then transports the pigment into the appropriate location within the skin.
This microscopic image clearly depicts the difference between the epidermis and the dermis. The net-like, outermost layer on the surface of the skin, called the stratum corneum, mainly consists of dead skin cells. Tattoo needles go through the epidermis and into the dermis where the ink is deposited.
What Makes Tattoos Permanent?
Skin cells live for about two to three weeks, but tattoos are permanent. The tattoo needles that have ink on the ends puncture the skin anywhere between 50 to 3,000 times per minute. The needle traverses the epidermis and goes into the dermis. An immune response is activated as a result of all the pinches from the tattoo needle. Every time this needle punctures the skin, macrophage cells are recruited towards to wound to try and close it. Macrophages are a type of white blood cell of the immune system that engulfs and digests cellular debris, foreign invaders, microbes, and cancer cells. Ink is an example of a foreign invader, an immunology term that describes anything that goes into the body that doesn't naturally belong there. The macrophage cells consume foreign substances (in this case the ink) to try and get rid of it. Ultimately, these macrophage cells full of ink get stuck in the gel-like matrix of the dermis and remain there.
Immediately after getting a tattoo, the ink is in both the epidermis and the dermis layers of the skin. As the skin heals, the wounded epidermal cells are shed and replaced with new, ink-free, cells. This is why tattoos look more vibrant before it is done healing. The epidermis regenerates after two to four weeks. Over longer periods of time, tattoos will fade as the body's immune system very gradually breaks down the pigment particles. The macrophages containing the ink takes them away to be degraded and destroyed. Overall, the the ink will stay with you for the vast majority of your life.
How Safe Are Tattoos?
There are several risks involved with both the tattoo inks and the application process. The most common of these risks is that of an infection. Allergic hypersensitivity, auto-immune reactions, granulomas, and interference with medical diagnosis and treatment can also result from getting a tattoo. From a chemical standpoint, there are more than 200 colorants and additives in use today to produce tattoo inks, and their long-term outcome in the body is not well understood. About half of tattoo pigments contain azo pigments, which have azo compounds. These compounds contain nitrogen-nitrogen double bonds that are known to release carcinogenic aromatic amines (aniline, anisidine, and toluidine) when they degrade, particularly when exposed to ultraviolet radiation (which we received plenty of from sunshine). Although there is no federal standard, distributors of quality inks now provide a list of ingredients used in their products along with information about the conditions of use and other warnings. Despite these risks, tattoos remain a part of our culture and have had major applications in societies across the globe. Hopefully more research can be conducted on tattoo pigments in order to use compounds that are safe for the body.
Sudan Red G is one of many different azo pigments that produces a reddish-orange color. The N = N double bond in Sudan Red G is split, yielding 1-amino-2-naphthol and o-anisidine. 1-amino-2-naphthol is a known human carcinogen, and o-anisidine is a dangerous environmental pollutant and a possible carcinogen.
