Two patients failed to show erythema from topical-contact sensitization in areas depigmented by para-tertiary butylphenol. However, the depigmented areas responded with erythema to both mumps skin test antigen and histamine phosphate administered intradermally. No cause could be determined for the topical unresponsiveness of the depigmented areas; a lack of response to contact sensitization was not seen in patients with vitiligo.
Kahn G. Topical Unresponsiveness of Depigmented Areas. Arch Dermatol. 1970;101(6):662-663. doi:10.1001/archderm.1970.04000060034008