For what it's worth, I found a chlorhexidine product that supposedly doesn't stain, or have other negative side effect normally associated with chlorhexidine. It's called Curasept. I see it available in the UK but I don't know about other countries. I live in the US.

Squamous cell carcinoma base of tongue. Lymph involvement unclear; staging placed at "2 or 3." Biopsy 4/18/2008. Treatment: IMRT every day for 7 weeks. Cisplaten once a week to sensitize cancer to radiation. Treatment ended 7/16/08. PET/CT shows no more cancer.