Povidone iodine allergy is very rare but has been reported. Skin testing with undiluted (25mg/ml) solution has been reported but the predictive value of positive and negative testing is not defined (Gray). Other topical antiseptics, notably chlorhexidine, have also been associated with systemic reactions, particularly when applied to disrupted or injured epithelial surfaces. One report suggests that over 9% of perianesthetic anaphylaxis may be related to chlorhexidine sensitivity (Opstrup).
Iodine as an antigen or component of radiocontrast dyes is not related to radiocontrast reactions. Therefore, there is no relationship between radiocontrast sensitivity and povidone iodine.
In summary, povidone iodine is a rare cause of allergic or allergic-like reactions. Prick skin testing has been reported using a concentration of 25mg/ml (undiluted) [Gray]. Chlorhexidine may also cause systemic reactions, but there is no cross-reactivity between chlorhexidine and povidone iodine. Radio contrast reactions are not related to iodine allergy. There is no concern about possible cross-reactivity between radiocontrast and povidone iodine.
Recurrent anaphylaxis caused by topical povidone-iodine (Betadine). Gray PE, Katelaris CH, Lipson D. J Paediatr Child Health. 2013 Jun;49(6):506-7
Standardized testing with chlorhexidine in perioperative allergy--a large single-centre evaluation. Opstrup MS, Malling HJ, Krøigaard M, Mosbech H, Skov PS, Poulsen LK, Garvey LH Allergy. 2014;69(10):1390.
I hope this information is of help to you and your patient.
All my best.
Dennis K. Ledford, MD, FAAAAI