Poisons, it is the homeopathic principle of remedies.
The principle, it is to give to your body a poison or a virus in small quantity so that your immune system develops an anti poison or an anti virus.
If to disinfect you your body, your immune system will never can developed by antibodies.
That is why, in 2012 so many people are allergic to all which moves.
People do not give the luck(chance) to the immune system to develop anti-allergies.
Most of us with rudimentary knowledge of the human immune system understand the way antibodies work. But that process doesn't applied to chemical compounds. I guess tolerance can be built, as in the case of alcohol, but that substance is metabolized.