Being skeptic of homeopathic methods is good. However, the desensitization process is not a homeopathic remedy at all (even though stores that sell homeopathic stuff will often carry it). It is a tried-and-true method that my doctor highly recommends. It has a specific mechanism by which it can work. So it definitely is a valid method.
I know some people just have such a severe reaction to it that this method doesn't help. But for people with a moderate or mild reactions using pills like this can definitely help.
I tried a military version of "poison ivy vaccine" years ago. I got the worse case of poison ivy that season that I would not wish on my worse enemy. I hope technology has proceeded in the right direction. I would be interested in the results.