Hi Kaz,

I would suggest building his immunity with a natural supplement which includes a full spectrum of digestive probiotic flora (immunity begins in the gut) and organic unprocessed foods. The probiotics (frinedly bacteria) are particularly important if he has been exposed to antibiotics.

Google MiEssence InLiven to see what I'm talking about. My boys have had exceptional health since they started taking it on a regular basis. My eldest has not had so much as a sniffle in 11 months now (he's only 3), despite regularly being around kids with runny noses, coughs etc at playgroup. It's certainly true that many parents do not honour the quarantine method of infection control for their children, which is a real shame - so you may wish to be cautious of such places whilst DH goes through his treatment. Is your DH also undergoing complementary treatment to support his allopathic treatment? Research supports the success rates for cancer treatment that is supported/complemented by natural therapies/intensive nutritional regimes. Some Naturopath's specialise in this field, and there are quite a number of oncologists who now recommend complementary treatment too - particularly the intensive nutritional element.

As a side note, you may be interested in the book Chemical Free Kids by Sarah Lantz, and apply the principles of the book in your home to limit your exposure to immunity-killing substances. You may also be interested in the book listed in my sig. Over 1000 referenced studies in there about vaccination. I personally believe that strengthening the immunity of the host (the person) via natural means is the single greatest defence against disease, next to sanitation. It has certainly been the case in my (unvaxed) family! :-)
Best wishes to your family as you go through this difficult time.