A white woman developed allergic contact dermatitis from neutral red chloride which had been applied to the skin for herpes simplex of the nose in three episodes during three months. She also had contact dermatitis of the skin of the foot from contamination with the dye. The patient's patch test to the dye, which she had used in a 3% aqueous solution, was strongly positive. A patch test given to five control subjects was negative.
Mitchell JC, Stewart WD. Allergic Contact Dermatitis From Neutral Red Applied for Herpes Simplex. Arch Dermatol. 1973;108(5):689. doi:10.1001/archderm.1973.01620260037013