we had a friend who learned that he was allergic to nightshades...

pretty traumatic for an Italian who grew up on tomatoes & eggplant.

For an unlucky few it seems that the chemicals have adverse affects.

from site listed below:
One of the major problems attributed to nightshades is arthritis. In fact, one in three arthritics will react badly to nightshades. Some researchers believe that arthritis is often misdiagnosed in people who may in fact only be experiencing the effects of nightshade consumption.

Alkaloids appear to affect the metabolism of calcium. Though not yet understood how, nightshade foods may remove calcium from bones and deposit it in soft tissue, setting the stage for arthritis. For this reason, researchers have recommended that all individuals with osteoarthritis, rheumatoid arthritis or other joint problems like gout eliminate nightshade foods from their diet.



Learn more: http://www.naturalnews.com/027978_nightshade_vegetables.html#ixzz36nmBk7TW