As I mentioned in the About Me section, I'm highly sensitive to lectins. In fact, much of Loren Cordain's latest work has been in highlighting the danger of this particular toxin in the formation of autoimmune disease -- a very scary thought. Lectins are present in many foods, but are found at toxic levels in the following:
Grains (wheat, rye, barley, malt)
Legumes (soy, peanuts, beans)
Nightshades (potatoes, tomatoes, peppers, eggplant)
You can find an extensive scholarly discussion here.
And a video of Loren Cordain himself discussing both the background of the paleo diet and the science behind the dangers of lectins (this is part 1 of 7, you can link to the rest from Youtube):
