Contact allergy to local anaesthetics-value of patch testing with a caine mix in the baseline series

Contact allergy to local anaesthetics is relatively common. Patch testing with benzocaine in the European baseline series is recommended for diagnosis, even though a caine mix has been previously suggested to be superior.

To assess the frequency and patterns of contact allergy to local anaesthetics by using a caine mix (benzocaine, tetracaine, and cinchocaine) in the baseline series, and evaluate its efficiency as compared with benzocaine alone.

We reviewed the results of 2736 patch tests performed between 2000 and 2010, identifying patients with positive reactions to caine mix or to one of seven local anaesthetics.

One hundred and twelve patients (4.1%) had at least one allergic reaction to local anaesthetics; 86 were tested with all seven local anaesthetics, resulting in 71 reactions in 53 patients. Cinchocaine gave the most reactions (50.7%); these occurred as a single reaction in 83.3% of patients, mostly with current or past relevance (97%). Benzocaine represented 22.5% of reactions, many of which were non-relevant (44%) or resulting from cross-reactions with para-compounds.

Almost 70% of allergic reactions to local anaesthetics would have been missed if benzocaine had been used as a screening allergen. This study supports a recommendation to replace benzocaine with a caine mix containing cinchocaine in the baseline patch test series.