A sensitizer is something that increases sensitivity or reaction to a particular stimulus or material. It can make a person or organism more likely to develop an allergic reaction when exposed to a certain substance.
If you're keen to do your own research, make sure you're looking at info (or reading sources that cite studies) published after 2012 as there seems to have been a bit of a spat in the scientific community concerning the use of insulin sensitizers for PCOS. (smartfertilitychoices.com)
Most individuals with PCOS are prescribed metformin as a form of insulin sensitizer for many metabolic and reproductive dysregulations. (pcosnutrition.com)
Title: OMX - 4.80 (Zox) a novel protein oxygen transporter and radiation sensitizer for dogs with oral melanoma (vetmed.ucdavis.edu)