Stability of fragrance patch test preparations applied in test chambers

Background: Petrolatum patch test preparations are for practical reasons often applied in test chambers in advance, several hours or even days before the patient is tested. As many fragrance compounds are volatile it may be suspected that petrolatum preparations applied in test chambers are not stable over time. Objectives: To investigate the stability of petrolatum preparations of the 7 chemically defined components in the fragrance mix (FM I) when stored in test chambers. Material and methods: Samples of petrolatum preparations applied in test chambers stored at room temperature and in a refrigerator between 4 and 144 h were analyzed using liquid chromatographic methods. Results: The concentration decreased by ≥20% within 8 h in 4 out of 7 preparations stored in Finn chambers at room temperature. When stored in a refrigerator only the preparation of cinnamal had decreased by ≥20% within 24 h. The stability of preparations of cinnamal stored in IQ chambers with a plastic cover was slightly better, but like the preparations applied in Finn chambers, the concentration decreased by ≥20% within 4 h at room temperature and within 24 h in a refrigerator. Cinnamal and cinnamyl alcohol were found to be more stable when analyzed as ingredients in FM I compared to when analyzed in individual preparations. Conclusions: Within a couple of hours several fragrance allergens evaporate from test chambers to an extent that may affect the outcome of the patch test. Application to the test chambers should be performed as close to the patch test occasion as possible and storage in a refrigerator is recommended.