The Art and the Science of Tattoos

Tattoos are a common and more accepted form of permanent personal adornment, with approximately 30% of the US adult population having at least 1 tattoo.¹ The practice of tattooing is more than 5000 years old, with tattoos found on mummified remains from the Neolithic era. There are several forms of tattoos: professional tattoos with insoluble pigments placed 1 to 4 mm into the dermis to create artistic images, medical tattoos used to define radiation ports, and cosmetic tattoos or permanent makeup to pigment the lips and line the eyes. This article examines the science behind the art of tattooing.

Professional tattooing is done with a reciprocating needle cluster that enters the skin anywhere from 50 to 3000 times per minute. The needle is laden with ink available in a rainbow of colors to create images, words, symbols, or tribal stamps to honor a stage in life or a lost loved one, create a sense of belonging, etc. Sometimes a stencil is used to outline the design, and other times the tattoo artist will freehand the image. Usually, a thin needle is used to outline the design, followed by thicker needles to add color and shading. The ink deposited in the dermis is taken up by macrophages, neutrophils, or fibroblasts, which is why the tattoo lines may become blurred over time. About one-third of the ink remains in the epidermis and is sloughed as the tattoo injury heals, and about one-fourth of the ink migrates to lymph nodes draining the area. With time, about 60% to 90% of the ink is transported via the lymphatics to lymph nodes, lungs, spleen, and liver. There are some concerns that, over time, the chronic proinflammatory effect of tattoo pigment in the body can damage the immune system by weakening its ability to detect cancer cells and respond to bacterial infection.

Some patients may seek dermatologic care to properly heal their tattoos for optimal color retention. Skin care products are now available specifically for tattoo care. The skin should be thoroughly disinfected prior to the tattoo procedure; nevertheless, the skin should be inspected for infection or tattoo dye reaction. If there are no adverse reactions related to the tattooing procedure, the skin should be cleansed daily with an antibacterial soap and patted dry. The fresh tattoo should then be covered with a petroleum jelly-based ointment to prevent scabbing and pigment loss until healing is complete. The tattoo should be protected with sunscreen once healing has occurred. UV radiation can dull the tattoo colors during and after healing. Finally, tattoo colors are more vivid when the stratum corneum is well hydrated and free of skin scaling; thus, tattoo care products are available to moisturize the skin and optimize color.

There are a number of medical issues that may occur following tattooing. Infection has already been mentioned, but the trauma of ink injection can result in keloid formation. Allergy and granuloma formation may occur, especially due to red ink. Green and blue inks are the second most allergenic. Red tattoo ink can contain mercury sulfide, also known as cinnabar, or cadmium red. Blue ink contains aluminum cobalt oxide, and green ink contains chromium oxide. Remember that tattoo inks are not US FDA approved because they are considered cosmetics; however, there are restrictions in the European Union for the substances that can be used in dyes for tattooing and permanent makeup.

There are several techniques employed to create various tattoo effects. The first technique is known as lining. Here, the outline of the desired design is placed in the skin to create the foundation of the image with bold lines. Lining is followed by shading to add depth and contrast. There are 3 forms of shading: whip shading, pendulum shading, and stipple shading. Whip shading involves pulling the tattoo needle out of the skin quickly to create a pigment gradient in the skin with more pigment placed deeply and less pigment placed more superficially. Pendulum shading rocks the tattoo needle back and forth in the skin to create deeper color at the center with less pigment tapering into the surrounding skin. Finally, stipple shading involves pulling the tattoo needle in and out of the skin quickly to create lots of pigment dots for a softer color effect. To produce vivid color in an area, color packing is done in which the needle is moved slowly in a circular motion to deposit more pigment in a given area. The skin is generally stretched tight to prevent uneven lines with the needle held at a slight angle or perpendicular to the skin.

Tattoos are becoming increasingly popular in the US. Since tattooing is a dermatologic procedure, dermatologists should be familiar with tattooing techniques, adverse effects, and postprocedure care.

References

1. 32% of Americans have a tattoo, including 22% who have more than one. Pew Research Center. August 15, 2023. Accessed July 15, 2026. https://www.pewresearch.org/short-reads/2023/08/15/32-of-americans-have-a-tattoo-including-22-who-have-more-than-one/

Zoe Diana Draelos, MD, is a clinical faculty member in the Department of Dermatology at Duke University School of Medicine in Durham, North Carolina; president of Dermatology Consulting Services in High Point, North Carolina; and Dermatology Times’ editor in chief emeritus.