Contact sensitization to tree moss (Evernia furfuracea extract, INCI) is heterogeneous

Evernia prunastri (oak moss) and Evernia furfuracea (tree moss) are lichens from which natural extracts are obtained.

To identify possible subgroups of E. furfuracea-sensitized patients according to whether these are allergic to lichen components or to contaminants.

A retrospective analysis was performed of surveillance data collected by the Information Network of Departments of Dermatology (www.ivkd.org) in 2003-2010 with oak moss absolute (1% pet.), tree moss absolute (1% pet.), and colophonium (colophony, 20% pet.).

In total, 3030 patients had been tested with all three allergens. Positive reactions to E. furfuracea were observed in 6.37%, to E. prunastri in 5.71%, and to colophonium in 4.82%. Concordance between positive reactions to E. prunastri and E. furfuracea was good only in patients not co-sensitized to colophonium (Cohen's κ = 0.681, 95% confidence interval 0.615-0.746). Moreover, E. furfuracea-sensitized patients showed (strong or extreme) concomitant reactions to colophonium significantly more often if not co-sensitized to E. prunastri.

Two subgroups of E. furfuracea-sensitized patients are identifiable: (i) those with sensitization to (oxidized) resin acids, as indicated by positive patch test reactions also to colophonium, and (ii) those non-sensitized to resin acids, but sensitized to common constituents of E. prunastri and E. furfuracea.