I agree with chepie on the Inner Health Immune Booster for kids, great stuff!! You can get it from most health food stores, I think it's about $20 a bottle but should last a while. You will find it in the fridge not with the vitamins. Another really good supplement in helping to build the immune system is Olive Leaf Extract, also from your health food store. And brauers recovery tonic when sick also as previously suggested. Cleaning hands and face is good but try not to be too clean as this will have the opposite effect.

A few books I highly recommend are Immunity foods for healthy kids by Lucy Burney and Healthy Living: Superfoods For Healthy Kids also by Lucy Burney. See if your local library has copies and borrow them for a few weeks. I think you can also get them on line if you want to keep them.

As your DS has been bombarded with one illness after another and so his immune system is constantly in a weakened state. As marcellus suggested you may want to consider having a break from all 'kid' social activities - swimming, playgroup etc for just a couple of weeks or a month so that your DS's immune system is given a chance to build up a bit of strength again. I have found this to be extremely helpful.

With regards to the suggestion of not cleaning the house too often, on some levels I agree and others I disagree. I think marcellus (please correct me if I have misunderstood) was suggesting this as exposure to certain bacteria is helpful in building a healthy immune system, in fact it is a requirement. On this level I definitely agree. The reason I also disagree is that household dust is toxic. Everything in our homes is made from chemicals, some of them highly toxic. For the most part they stay where they are supposed to but some of them, particularly flame retardant chemicals, escape into the air and attach to dust particles which then settle on the floor, furniture etc. The problem with this is that our kids then come into contact with these chemicals and they are absorbed into their bodies in a number of ways. Through breathing them, skin contact and through the mouth (how many kids do you see with toys/objects/fingers in mouth). Dusting is often a chore that is often hated but it is also one way we can reduce our exposure to toxic chemicals in homes. Always use a damp cloth because the more you 'disturb' the dust and make it airborne the more you (and your kids) are breathing it in.

Sorry about the long winded reply