Sometimes regrettable yet increasingly common, tattoos are an ancient art form used in modern times as a mark of artistic and cultural expression. Allergic contact dermatitis (ACD) to tattoo ink is rare, but the popularity of tattoos makes ACD an increasingly recognized occurrence. In a retrospective study of 38,543 patch-tested patients, only 29 (0.08%) had tattoo-related ACD, with the majority of patients being female and young adults. The most common contact allergy was to paraphenylenediamine (PPD), which occurred in 22 (76%) patients.1 In this article, we will walk you through the rainbow of tattoo ACD, covering hypersensitivity reactions to both temporary and permanent tattoo inks.
Temporary Tattoo Inks
Henna is the most common temporary tattoo ink. Derived from the plant Lawsonia inermis, henna is an orange dye that has been used in many parts of the world, particularly in Islamic and Hindu cultures, to dye skin, hair, and fabrics. Application of henna tattoos is common for weddings and other celebrations, and brides may wear elaborate henna patterns. To create these tattoos, henna powder is mixed with water and sometimes essential oils and is then applied to the skin for several hours. After application, the henna pigment lawsone (2-hydroxy-1,4-naphthoquinone) interacts with keratin and leaves a red-orange stain on the skin2; longer application time leads to a deeper color. Most traditional cutaneous henna designs fade in 2 to 6 weeks, but some last longer. Red henna generally is considered safe with low incidence of contact allergy. What is referred to as black henna usually is red henna mixed with PPD, a black dye, which is added to deepen the color. Paraphenylenediamine is highly sensitizing; patients can become sensitized to the PPD in the tattoo itself.2 One study confirmed the presence of PPD in black henna tattoos, with chemical analysis of common preparations revealing concentrations ranging from less than 1% to 30%.2 Patients who undergo patch testing for tattoo reactions often are strongly positive to PPD and have concomitant reactions to azo dyes, black rubber, and anesthetics. Other aromatic amines including aminophenols have been identified in black henna tattoo ink, and these chemicals also may contribute to ACD.3 Less common sources of contact allergy from temporary black henna tattoos include resorcinol,4 para-tertiary butylphenol formaldehyde resin,5 and fragrance.6
Clinically, ACD to PPD in temporary tattoos presents 1 to 3 days after application if the patient is already sensitized or 4 to 14 days if the patient is sensitized by the tattoo ink.2 Most patients notice erythema, edema, vesicles, papules, and/or bullae, but other less common reactions including generalized dermatitis, systemic symptoms, urticaria, and pustules have been described.2 Postinflammatory hypopigmentation or hyperpigmentation also can occur.
Because of the sensitizing nature of black henna tattoos, consumers are turning to natural temporary tattoos. Jagua temporary tattoos, with pigment derived from the sap of fruit from the Genipa americana tree, have been associated with ACD.7 This black dye is applied and washed off in a similar fashion to henna tattoos. Importantly, a recent analysis of jagua dye identified no PPD. In one case, a patient who developed ACD to a jagua tattoo was patch tested to components of the dye and had a positive reaction to genipin, a component of the fruit extract.7 Thus, jagua tattoos often are marketed as safe but are an emerging source of contact dermatitis to temporary tattoos.
Permanent Tattoo Inks
Permanent tattoos are created by injecting small amounts of ink into the dermis. As the name suggests, these tattoos are permanent. Tattoos are common; nearly one-third of Americans have at least 1 tattoo.1 Historically, tattoos were created using black pigment composed of amorphous carbon or black iron oxides.8,9 Metallic pigments (eg, mercury, chromium, cobalt, cadmium) were once used to add color to tattoos, but these metals are now only rarely used; in fact, a 2019 study of tattoo ink components identified 44 distinct pigments in 1416 permanent inks, with an average of 3 pigments per ink.8 Of the 44 pigments, 10 had metallic components including iron, barium, zinc, copper, molybdenum, and titanium. The remaining 34 pigments contained carbon, azo, diketopyrrolopyrrole, quinacridone, anthraquinone, dioxazine (purple), or quinophthalone (yellow) dyes. The authors noted that nearly one-quarter of the tattoo pigments identified in their study had been reported as contact allergens.8
Typically, reactions to permanent tattoo inks manifest as an eczematous dermatitis occurring weeks to years after tattoo application.9,10 The dermatitis usually is locally confined to the tattoo and may be limited to particular colors; occasionally, a new tattoo reaction may trigger concurrent inflammation in older tattoos. Many tattoo reactions occur as a response to red pigment but also have occurred with other tattoo ink components.9 Many researchers have speculated as to whether the reaction is related to the ink component itself or from the photochemical breakdown of the ink by exposure to UV radiation and/or laser therapy.9
Red Pigment
Red ink is the most common color reported to cause tattoo hypersensitivity reactions. Historically, red tattoo pigments include mercuric sulfide (vermilion, cinnabar), scarlet lake, cadmium red, carmine, and cochineal,11 but today’s tattoo inks primarily are composed of other pigments, such as quinacridone and azo dyes.12 Several cases of red tattoo ink hypersensitivity reactions exist in the literature, many without completion of patch tests or without positive patch tests to relevant red pigments.11-15
Black Pigment
In general, reactions to permanent black tattoo ink are rare; however, a few case reports exist. Black pigment can be created with India ink (carbon), logwood (chrome), iron oxide, and titanium.16,17 Shellac can be used as a binding agent in tattoo ink; there is at least one report of a reaction to black tattoo ink with a positive patch test to shellac and the original black ink.18