The concept of "compartment allergy": prilocaine injected into different skin layers

Interestingly, our patient repeatedly tolerated strictly deep subcutaneous injection of prilocaine in provocation testing while patch and superficial subcutaneous application mounted strong allergic responses. We hypothesize, that lower DC density in deeper cutaneous compartments and/or different DC subsets exhibiting distinct functional immunomodulatory properties in the various layers of the skin may confer to the observed absence of clinical reactivity against prilocaine after deep subcutaneous injection.The term compartment allergy indicates that the route of allergen administration together with the targeted immunologic environment orchestrates on the immunologic outcome: overt T-cell mediated allergy or clinical tolerance.Local anesthetics (LA) are extensively used drugs with a safe application profile and only rare objective side effects. Most reported adverse reactions can be attributed to inherent pharmacological and toxic effects of the LA - especially after applying high doses or in case of accidental intravasal injection - as well as psychovegetative disturbance merely due to the painful procedure. Immune-mediated reactions comprise less than 1% of all adverse LA reactions whereby true IgE-mediated allergic reactions to LA are very rare - if they occur at all [1,2].Delayed-type hypersensitivity reactions to LA are thought to occur more commonly than immediate reactions. The diverse antigenic determinants of the different LA substance groups (esters, amides) and their metabolites as well as the exact immunologic mechanisms involved in delayed-type reactions to LA are partially elaborated. Therefore, putative cross-reactivity between the different substance classes can be predicted merely from the LA structure. Allergic reactions are most often caused by ester compounds of LA putatively because of its metabolite paraaminobenzoeacid (PABA) as the relevant antigenic structure [3]. Delayed-type hypersensitivity against LA may be acquired by different exposure