tomato/potato are obvious. But what else should I avoid? The best list I’ve found is at the World’s Healthiest Foods. I find the name ironic, but it is helping me get healthier.
The most famous food members of the nightshade family include potatoes (Solanum tuberosum), tomatoes (Lycopersicon esculentum), many species of sweet and hot peppers (all species of Capsicum, including Capsicum annum), and eggplant (Solanum melongena). Less well know, but equally genuine nightshade foods include ground cherries (all species of Physalis), tomatillos (Physallis ixocapra), garden huckleberry (Solanum melanocerasum), tamarillos (Cyphomandra betacea), pepinos (Solanum muricatum), and naranjillas (Solanum quitoense). Pimentos (also called pimientos) belong to the nightshade family, and usually come from the pepper plant Capsicum annum. Pimento cheese and pimento-stuffed olives are therefore examples of foods that should be classified as containing nightshade components. Although the sweet potato, whose scientific name is Ipomoea batatas, belongs to the same plant order as the nightshades (Polemoniales), it does not belong to the Solanaceae family found in this order, but to a different plant family called Convolvulaceae.
The seasoning paprika is also derived from Capsicum annum, the common red pepper, and the seasoning cayenne comes from another nightshade, Capsicum frutenscens. Tabasco sauce, which contains large amounts of Capsicum annum, should also be considered as a nightshade food. It may be helpful to note here that black pepper, which belongs to the Piperaceae family, is not a member of the nightshade foods.
Other relevant posts:
Discussion of solanine in nightshades and how it isn’t really an allergy. But it acts like one. “A rose by any other name would smell as sweet.” And an allergy by any other name hurts.
A collection of internet comments on nightshades that were relevant to me or my family.
Night Shade Allergies, my post with the most comments, I think.