I've been having digestive trouble recently and have started wondering if I've developed a new allergy/intolerance (Known: milk, cashewnuts, chocolate). Does anyone have a recommendation for tests to check for these?

Apparently, "Eight foods account for 90% of all food-allergic reactions: milk, eggs, peanuts, tree nuts (e.g., walnuts, almonds, cashews, pistachios, pecans), wheat, soy, fish, and shellfish." (source: http://www.foodallergy.org/file/facts-stats.pdf). However, nuts are good for you (eg. https://examine.com/faq/how-can-i-best-ensure-cardiovascular-health-and-longevity/). So what do you do?

I imagine allergies are bad for your body, even apart from the digestive issues. So, do you take any supplements for nuts? The only one I am aware of here is Omega-3, which is common to various nuts.

Sidenote: If you are willing to put a "nuts without allergies" supplement together, I might buy it from you. See https://www.reddit.com/r/Supplements/comments/3ptsz8/i_am_a_supplement_caffeineenergy_pill_company/cw9gwht for business advice.