Black-spot poison ivy dermatitis

Hogan DJ (1996) The prognosis of irritant contact dermatitis. In van der Va PGM, Maibach HI (eds) The irritant contact dermatitis syndrome. CRC, New York, pp 9-15 Hogan DJ, Dannaker CJ, Maibach HI (1990) The prognosis of contact dermatitis. J Am Acad Dermatol 23 300-307 Hurwitz RM, Rivera HP, Guin JD (1984) Black-spot poison ivy dermatitis. An acute irritant contact dermatitis superimposed upon an allergic contact dermatitis. Am J Dermatopathol 6 319-322... 

Sometimes a black deposit resembling black enamel paint can be seen at the sites of injury of poison ivy, poison oak and poison sumac. This is a hardened form of the allergenic sap on the surface of the plant. The black material is not as irritating as the clear liquid sap, but it is still very allergenic. After prominent exposure to the plant, one occasionally finds black spots on the skin in the areas of the dermatitis (Fig. 7). This is called black-spot poison-ivy dermatitis [46]. The tendency for the sap to turn black can help to confirm the identification of poison ivy, poison oak and poison sumac in the field [45]. The directions for doing this are found in Table 2. 

Mallory SB, Hurwitz RM (1986) Black-spot poison-ivy dermatitis. Clin Dermatol 4 149-151... 

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