FIGURE 1 (A), Prurigo nodularis-like eruption. (B), leg ulcer surrounded by eczematous reaction. (C), positive patch test reaction to chloramphenicol on day 2ROMITA ET AL. 251 of Allergological Professional and Environmental Dermatology (SIDAPA) baseline series (Euromedical, Calolziocorte, Italy) and the topical ointment (Iruxol, tested "as is") were performed. Patch tests were applied on the back and left under occlusion for 2 days with Al Test (Euromedical) on Scanpor tape (Norgesplaster, Vennesla, Norway).Readings were performed on day (D) 2, D4 and D7 according to ESCD guidelines, and showed a positive reaction to Iruxol. Subsequently, patch tests with chloramphenicol 5% pet., Noruxol "as is" (containing only clostridiopeptidase A) and ingredients of both ointments (liquid paraffin and white pet.) were performed, and showed a positive reaction to chloramphenicol ( Figure 1C). No recurrence at 1-year follow-up was observed.
| DISCUSSIONChloramphenicol was first reported as a contact sensitizer in 1961. 3The prevalence of chloramphenicol contact sensitivity in a large group of patients with venous leg ulcers was reported to be 12.0%. 1 Here, we report contact sensitivity to chloramphenicol with extensive prurigo nodularis-like spreading appearing in areas where the chloramphenicol-containing ointment had not been applied. Spreading of eczema to adjacent and distant regions was described as "autoallergy" by Parish in 1965. 4 Recently, unusually extensive and noneczematous spreading caused by a topical medication was described. 5Regarding the spreading induced by chloramphenicol, only two cases of maculopapular exanthema and one case of acute generalized exanthematous pustulosis have been reported. 6 To the best of our knowledge, this is the first report of prurigo nodularis-like spreading associated with contact allergy to chloramphenicol. The occurrence of prurigo nodularis as result of ACD has been studied in the past 7 ; prurigo nodularis-like lesions have rarely been described at the site of direct contact only, associated with contact allergy to nifuroxazide, 8 parthenium, 9 pyridine, 10 and p-phenylenediamine. 11
CONFLICTS OF INTERESTThe authors have no conflicts of interest to report.
ORCIDPaolo Romita https://orcid.org/0000-0002-5559-9722Luca Stingeni https://orcid.org/0000-0001-7919-8141