If you're talking about de(hypo)sensibilization, then it does not work. At least not reliably and permanently. Been through it as a kid when it was the newest and hottest thing. Five years later after evaluation of long term data I got an excuse from my doctor and found out that general health insurance in Germany wasn't covering it anymore and the allergologic's associaton was not recommending it. That's about as close to an official, big, red "scam!" sign as at gets.