Can topical zinc accentuate tuberculin reactivity in the elderly?

We examined the effect of topical zinc on Heaf tests in 58 elderly hospitalized patients in a double-blind study. Plasma zinc levels were measured. Thirty-eight subjects (66%) had negative reactions with placebo ointment. Fourteen of these negative responders (37%) had positive reactions with topical zinc ointment; 12 (32%) had weakly positive reactions and 12 remained negative. There was no significant difference in the plasma zinc levels between the different grades of topical zinc effect in the negative responders. Zinc deficiency is therefore unlikely to account for the observed booster effect of topical zinc on tuberculin reactivity.