I just re-read your signature. Chemo can cause bad breath and also leave a very strong chemical like body odor (especially if you are getting Cisplatin). Chemo also does a number on the stmach lining as well so anti acids may help, since a lot of bad breath issues are stomach related. I don't believe that you want the type with magnesium though, stick with Famatodine (Pepcid AC). Get a prescription so you don't have to buy it over the counter.