| Score | Interpretation | Tips and advice |
| - | Negative reaction | |
| ? or +/- | Doubtful reaction, faint erythema | Caution with interpretation, especially with less common allergens. Consider repeat testing or follow-up with ROAT testing. |
| + | Weak reaction, erythema, slight infiltration | Erythema should be palpable and occupy >50 percent of patch test site. |
| ++ | Strong reaction, erythema, infiltration, vesicles | Look for microvesicles to occupy at least 50 percent of the patch test site. |
| +++ | Extreme, bullous, ulcerative | Confluent vesicles. |
| IR | Irritant reactions | There is a broad range. Mild irritant reactions have a glazed appearance. Moderate reactions are follicular (pustular in atopics). Extreme reactions can be ulcerative. |
| NT | Not tested |
