Table 1 Criteria for human skin patch test by International Contact Dermatitis Research Group
| Symbol | Score | Result |
|---|---|---|
| − | 0 | Negative |
| ± | 0.5 | Doubtful or slight reaction and erythema |
| + | 1 | Erythema + Induration |
| ++ | 2 | Erythema + Induration + Vesicle |
| +++ | 3 | Erythema + Induration + Bullae |