Normal skin test responses in chronic marijuana users.

The cell-mediated immunity of 22 chronic marijuana smokers showed no difference from that of normal controls when evaluated by in vivo skin testing with 2,4-dinitrochlorobenzene. However, a significant difference was seen between these chronic marijuana users, all of whom could be sensitized to 2,4-dinitro-chlorobenzene, and age-matched cancer patients, who showed a decreased capacity to be sensitized.