White petrolatum (Ph. Eur.) is virtually non‐sensitizing. Analysis of IVDK data on 80 000 patients tested between 1992 and 2004 and short discussion of identification and designation of allergens

Sporadic cases of contact allergy to white petrolatum, which is used as a vehicle in patch test preparations, have been reported. The quantitative relevance of the phenomenon remains yet to be elucidated. Methods : Retrospective analysis of patch test data of the Information Network of Departments of Dermatology (IVDK, http://www.ivdk.org ) between 1992 and 2004. Results : Analysis of 79 365 patients patch tested with pure petrolatum yielded 27 ‘+’ (0.03%) and 2 ‘+++’ (0.003%) reactions. The majority of non‐negative reactions (0.3%) was interpreted as doubtful (235) or mild irritant (32). The negative reaction index (RI) (−0.8), and the high positivity ratio (PR) (93%) especially a lack of concordance with patch test preparations containing ≥99% petrolatum indicate that many of the ‘positive’ (+) reactions have to be considered as irritant. There were 2 ‘+++’ reactions. In 1 case, an ‘angry back reaction’ was confirmed. The other case is probably a reading or documentation error, as the majority of patch test reactions to preparations containing petrolatum remained negative in this case also. Conclusions : True allergic patch test reactions to white petrolatum are extremely rare and probably due to an individually increased susceptibility to allergens and/or irritants. This is in agreement with considering petrolatum as a non‐sensitizer.