[Diphenylcyclopropenone - a new strong contact sensitizer (author's transl)]

A new synthetic substance - diphenylcyclopropenone - has been proven to be responsible for contact dermatitis in three persons handling it in chemical laboratories. A student of chemistry developed a dermatitis of the hands that lasted for more than two months. Based on the case history this dermatitis was considered to be an allergic one. The sensitizing capacity of diphenylcyclopropenone was proven experimentally in guinea pigs by use of the open epicutaneous sensitization method. All 25 animals became strongly sensitive. Sensitization could also be induced by a single application of low concentrations, for example with 3% in acetone. Cross-reactions could be elicited in the sensitized animals by intermediate produts and the synthesis like alpha, alpha'-dibromdibenzylketone and the remaining procduct called "red oil". The intermediate product is a mixture of racemic d- and l-forms and a meso-form as well, whereas the "red oil" consists of polymerized carbonyl compounds, from which diphenylcyclopropenone is extracted with boiling cyclohexane. Risk of contact with the sensitizer is greatest in the last step of synthesis. Care should not only be taken while handling this new substance in chemical laboratories, but contact should also be avoided with the intermediate and end products in cases where a diphenylcyclopropenone contact allergy is present.