Scientific Perspective on Tattoos

Tattoo Ink is Something of a Mystery

Manufacturers of tattoo ink aren’t required to reveal their contents – the ink is not regulated by the FDA or other agencies. Many professional tattoo artists mix their own ink from dry pigments, but contents might not be revealed to a client for competitive reasons.

Tattoo “inks” aren’t really inks – they are pigments suspended in a carrier solution. Most inks are made of metal salts. Some are plastics, some might be vegetable dyes.

One concern with tattoo ink is what is in the ink besides the carrier solution and the dyes. If a tattoo shop doesn’t adhere to safety precautions, a range of infections (especially hepatitis) might be contained in tattoo ink if the tattoo artists dips the needle in an infected person, back in the ink container, then into a new client’s skin. A variety of safety regulations are established by the state and local authorities that work to prevent this cross-infection.

Toxicity/Reaction with Tattoo Ink

Some chemical reactions exist between skin and tattoo ink. You can look at the Material Safety Data Sheet for the pigment or carrier to see what some of the interactions might be. Allergic reactions, scarring, phototoxic reactions (i.e. reactions from sunlight and other light) are possible.

Plastic-based pigments can be intensely colored and very difficult to remove. Some inks glow-in-the-dark in response to black (ultraviolet) light, some of these are safe, but some are radioactive or toxic. The lack of regulations on tattoo ink make out-of-the-ordinary inks potentially risky; most standard tattoos will cause no visible reaction with the skin, with red ink the most common.

Tattoo Ink Carrier

Carrier keep pigment evenly distributed in a fluid matrix, inhibits the growth of pathogens, prevents clumping of pigment, and aids in the application to the skin.

Safest and Most Common Ingredients:

Ethyl alcohol (ethanol)

Purified water

Witch hazel

Listerine

Proplyene glycol

Glycerin

Scary stuff can be used, too

Denatured alcohol (toxic, can burn skin)

Other alcohols (methanol)

Antifreeze

Formaldehdye (very toxic)

What Tattoo Ink Is Made Of

Black Ink is made of Iron Oxide (Fe3 O4) or (Fe O), Carbon, Logwood

Natural black pigment is made from magnetite crystals, powdered jet, bone black, and amorphous carbon from combustion (soot). Black pigment is commonly made into India ink.

Logwood is a hardwood extract from Haematoxylon campechisnum, found in Central America and the West Indies

Red Ink is Cinnabar (HgS) or mercury sulfide, Cadmium Red (CdSe), Iron Oxide (Fe2O3), Napthol-AS pigment, Iron oxide is also known as common rust. Cinnabar and cadmium pigments are highly toxic. Napthol reds are synthesized from Naptha. Red ink carries risks of allergic or other reactions.

Blue Ink: Cobaltic aluminate (azure blue)

Green Ink: Chrome oxide (Casalis green), Hydrated chromium sesquioxide, Malachite green, Lead chromate, Ferro-ferric cyanide, Curcumin green, Copper salts with yellow coal tar dyes

Yellow Ink: Cadmium sulfide (cadmium yellow), Ochre

Violet Ink: Manganese violet

White Ink: Titanium dioxide, Zinc oxide

Flesh Colored Ink: Iron Oxides

Scientific Details on Tattoos

Tattoos are applied by injecting ink into a person’s skin. An electrically-powered tattoo gun punctures the skin between 50 and 3,000 times per minute and reaches a depth of up to several millimeters.

In tattoos, the ink particles (commonly 2-400nm with 40nm average) are embedded in a protein envelope. A prominent network of connective tissue surrounds each of the fibroblasts containing ink particles, effectively entrapping & immobilizing any cell. The lifespan of these fibroblasts is unknown and may persist for the life of the individual.

Where Is Tattoo Ink In the Skin

The tattooing process causes damage to the epidermis, epidermal-dermal junction, and the papillary layer (topmost layer) of the dermis.

The layers are homogenized (mush-like) right after the tattooing process.

One of the first responses of the body to tattooing is to stop the bleeding caused by broken capillaries that are leaking to the surface of the skin. The body’s autoimmune response will include swelling as cells such as neutrophils respond to the injury.

Neutrophils are phagocytic cells that clean up the area by swallowing the ink and flushing it through the lymphatic system.

The ink itself is initially dispersed as fine granules in the upper dermis, but gathers into more concentrated areas at 7-13 days.

What Happens to Ink After Tattooing

Tissue reforms around the tattoo pigment in the form of a re-vitalized epidermis, a strengthened epidermal-dermal junction, and ink is trapped in dermal fibroblasts

Fibroblasts are cells that are important in healing wounds and are the most common connective tissue in animals.

After a month the epidermal-dermal junction is in the process of reforming and cells that a trapping the ink are taking their positions in this region. Some ink is being eliminated through the epidermis.

The epi-dermal junction will be completely reformed within two to three months with the tattoo ink present in dermal fibroblasts surrounded by connective tissue that holds the ink in place.

Side Effects of Tattooing

Swelling, Redness, Tenderness: common for 24 hours to a week

Scabbing: somewhat common when skin punctured and bleeding results from tattooing

Possible infection (Hep-C, HIV, staph, etc.): rare, but possible when tattoo parlors do not follow safety protocols

Scarring/Raised Skin: common with unskilled tattoo artists, occurs when tattoo is applied too deeply and roughly

Allergic Reaction, esp. with red ink

How Tattoos Evolve In the Skin

Ink particles are moved into the deeper dermis over time due to the actions of mobile phagocytic cells (think immune cells) causing the ink to look bluish, faded, and blurry.

Examination of 40+ year old tattoos shows that the ink is in the deep dermis and also found in local lymph nodes.

With the presence of larger than normal amounts of migrating phagocytic cells, the chances of ink movement increases, thus accelerating the fading of the tattoo.

Some colors disappear completely with time: White, yellow, red, and flesh tones

Effects of Sun on Tattoos

During sun exposure many Langerhans cells undergo apoptosis (a type of cell death where cells break apart into many small fragments).

Other Langerhans cells migrate into the dermis and minor inflammatory reactions occur.

The inflammatory reaction is not restricted to the epidermis, but also involves the dermis. Such a reaction causes the recruitment of more phagocytic immune cells to the area.

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