Patch Testing
| Characteristic | Details |
|---|---|
| Testing site | Back or upper arm (needs to be hairless) |
| Testing reagents | 1% and 10% of reagent grade product; 10% and 30% of trade product; most commonly used vehicle is petrolatum |
| Controls | + None - Petrolatum |
| Shelf-life of patch test mixes | Most antibiotics at room temperature are stable for 1 to 3 months; check with USP Pharmacopeia for verification |
| Patches | Finn chambers (can be aluminum or molded plastic) |
| Tape | Use hypoallergenic paper tape |
| Reading | At 48 hours (85% of drugs-if will be positive-are positive by this point); 72 hours; 96 hours; and 1 week |
| Test interpretation | - Negative ? Doubtful reaction + Weak reaction, erythema ++ Strong reaction, erythema, papules, or vesicles +++ Extreme, bullous, ulcerative |
