Gluten cross-reactivity
Gluten cross-reactivity is of particular concern for anyone whose body produces antibodies against gluten, technically a gluten allergy or gluten intolerance. Essentially, when your body creates antibodies against gluten, those same antibodies also recognize proteins in other foods. When you eat those foods, even though they don’t contain gluten, your body reacts as though they do. You can do a fantastic job of remaining completely gluten-free but still suffer all of the symptoms of gluten consumption—because your body still thinks you are eating gluten. This is a very important piece of information that was missing until recently.
So what happens in cross-reactivity?
In this case the amino acid sequence that an antibody recognizes is also present in another protein from another food (in the case of molecular mimicry, that sequence is also present is a protein in the human body). There are only 20 different amino acids, so while there are millions of possible ways to link various amount of each amino acid together to form a protein, there are certain amino acid sequences that do tend to repeat in biology.
A recent study evaluated the potential cross-reactivity of 24 food antigens.
Foods That Don’t Play Nice With Gluten
Rye
Barley
Spelt
Polish Wheat
Oats (2 different cultivars)
Buckwheat
Sorghum
Millet
Amaranth
Quinoa
Corn
Rice
Potato
Hemp
Teff
Soy
Milk (Alpha-Casein, Beta-Casein, Casomorphin, Butyrophilin, Whey Protein and whole milk)
Chocolate
Yeast
Coffee (instant, latte, espresso, imported)
Sesame
Tapioca (a.k.a. cassava or yucca)
Eggs
Have you Given up gluten but still having symptoms?
Beyond this, gluten contamination is common in the food supply and many grains and flours that are inherently gluten free may still contain gluten once processed. Commonly contaminated grain products include millet, white rice flour, buckwheat flour, sorghum flour, and soy flour. As these are commonly used ingredients in commercial gluten-free baked goods, extreme caution should be exercised.
Cyrex Labs offers a simple blood test that is referred to as their gluten cross-reactivity panel, a.k.a. Array 4. It tests for reactions to the gluten cross-reactors mentioned above as well as the non cross-reactors evaluated in the paper.  Cyrex Labs reports positive sensitivities in many of those foods in people with diagnosed gluten sensitivity. This may reflect that when you have a leaky gut, food intolerances are quite easy to form.
If you have autoimmune disease (which has a very high correlation with gluten-sensitivity), celiac disease, gluten-sensitivity, or are simply not seeing the improvements you were hoping for by following a standard Paleo diet, one or all of these foods may be the culprit. Get tested and find out if the foods you are eating are still causing your problems- Learn more here