NR | Negative reaction |
? | Doubtful reaction (weak erythema only) |
+ | Weak positive reaction: erythema, induration, possibly papules |
++ | Strong positive reaction: erythema, induration, papules, vesicles |
+++ | Extreme positive reaction: intense erythema and induration, |
 | coalescing vesicles, bullous reaction |
IR | Irritant reaction |