Isosulphan blue is one of the most commonly used dye for sentinel lymph node biopsy in breast cancer patients with clinically negative axilla. Allergic reactions related to this dye are rarely observed and these reactions can be seen in a wide spectrum of clinical settings ranging from mild skin rashes to life threatening anaphylactic shock. A 52 year old post-menapausal woman, during the SLNB, disseminated blue coloured maculopapular skin rashes right after the subareolar injection of isosulphan blue dye occurred. This case has been reported because of its rare incidence and since it should be kept in mind that allergic reactions to this dye may take place following it’s injection during sentinel lymph node biopsies.