Patent blue V is widely used in the identification of sentinel lymph nodes in patients with
breast cancer and other
malignancies. Individual case reports of
allergy to
patent blue V have been described in the medical literature since the 1960s. However, there is little data on clinical features and little experience of which
allergy tests are appropriate or useful. We gathered all cases of
patent blue V allergy that had been seen and diagnosed in the Department of
Allergy, Addenbrooke's Hospital over a 3-year period. We collected clinical details of each case including skin test results. For comparison we recruited 12 healthy control subjects who then underwent skin testing to
patent blue V. Six cases of
patent blue V allergy were identified, all occurring during sentinel lymph node identification for
breast carcinoma. All 6 had positive skin prick tests to neat
patent blue V (25 mg/ml). Skin prick testing with a 1 : 10 dilution (2.5 mg/ml) produced positive results in 3 of 4 patients tested, and intradermal testing at a 1 : 100 dilution was (0.25 mg/ml) was positive in all patients tested. Of 12 control subjects, 11 had negative skin prick tests to both neat and 1 : 10
patent blue V with one subject showing a positive reaction to the higher concentration only. On the basis of our experience of
patent blue V allergy, we propose a diagnostic protocol that can be safely and reliably utilised in centres equipped for
allergy testing.