[Delayed type allergic reaction to red azo dye in tattooing].

Allergic reactions in tattoos are comparatively rare. In most cases the reactions are caused by different red pigments. While in the past these reactions have been ascribed to mercury salts (cinnebar) and cadmium sulphide, now synthetic inorganic azo dyes have also been found to be responsible for such reactions. A 42-year-old man presented with an allergic reaction in the red parts of his tattoos. Histologically a chronic granulomatous, partly fibrous inflammation with transfollicular elimination of pigment granules was found. Spontaneous regression in a part of the inflammatory reaction was observed, simultaneously with depigmentation and scarring of the overlying skin. The pigment used for tattooing was found to be an aromatic azo derivative. In addition to a positive cutaneous reaction to the dye, the patient also showed a positive patch test to Napthol AS, used for the coupling of different dyes in the textile industry.