What to ask a caterer or a really nice friend who wants to make/bake nut-safe foods...

THE QUESTION TO ASK:
Is there a risk of nut protein (even dust particle sized) in the food, either from actual ingredients or cross-contamination?  More specifically, from:
(a) residue* on equipment, prep area surfaces, prep or inadvertently shared serving utensils, or oven, or
(b) airborne dust** from nuts used in other foods being prepared in the same facility, or
(c) ingredients that may have hidden*** nut protein contamination, or
(d) processed ingredients that could have their own cross-contamination issues?

You can stop there and hope that they are informed enough to think that through.  I use the info below to answer their questions or nudge the conversation along so that all of the traps are run...

THE BACKGROUND DETAIL TO KNOW:
*As for residue - it's sufficient to scrub utensils, prep areas, pots/pans and stove/oven that may have touched nuts with soap and water.  Scrubbing with a "soap" (not sanitizer) is important to remove proteins cuz they are sticky.  Oven cleaning cycle isn't really sufficient because it incinerates what's in the oven but doesnt get rid of it, ... and nut proteins allergens are intensified when roasted and fly around more easily when in ash form.

**Airborne dust would be present in places like ice cream stores with open dishes of toppings, Chinese restaurant kitchens with lots of nuts and nut oil being cooked/burned and smoke resulting, a nut free manufacturing line adjacent to other lines that use nuts in their product, bakeries that use nut flour or nuts in anything.

***As for ingredients, some innocent items are actually hazardous for the person allergic to Tree Nuts and Peanuts:
(a) Bread/bread crumbs - is the bread potentially cross-contaminated?  Is the manufacturer's policy to disclose even potential cross-contamination?  (Not all manufacturers do this - It seems that only the largest manufacturers face enough potential liability that they voluntarily do this.) Artisan breads are nearly always off limits for ingredients and facilities.
(b) Flavorings - almond extract is not safe, but artificial almond extract may be safe.  Some vanilla extract is not safe because it's made in the same facility/on the same equipment as a nut extract.
(c) Chocolate - many chocolates are flavored with nut extracts or are made on equipment that also makes chocolates containing nuts.  Usually, pure cocoa powder is safe though.  Examples: Hershey's plain kisses are ok, Tollhouse chips are not, Nestle Crunch bars are not, Trader Joe's chocolate chips are ok but their white chocolate chips are not (last I checked).
(d) Spices - some spice mfr's also process nuts and seeds.  McCormick's tells me to avoid any of their blends, but that single spices are ok.
(e) Processed ingredients (e.g. tahini, international cuisine sauces, pre-seasoned items) are often potentially cross-contaminated.
(f)  Bulk bin ingredients are very risky.
(g) Local small producer ingredients often risk cross-contamination and I avoid them - they share equipment and have always been unable to speak to whether other users have left nut residue.  They are also exempt from detailed labeling laws that apply to large mfrs.  (e.g. Bob's Red Farm flours are made on shared equipment)  I stick with major food manufacturers that face enough risk of liability that they disclose potential cross-contamination.
(h) Anything baked in a commercial facility, unless that facility does not use any peanuts or tree nuts or ingredients that contain peanuts or tree nuts.
(i) If you can wash it with agitation, a food cleaning agent and water, it will be ok (e.g. raw fruits/vegs).
(j) Foreign made ingredients or foods - I avoid because they are not subject to all US labeling laws, and do not usually disclose risks of cross-contamination.
(k) Mixes - if from a big manufacturer, you can generally rely on the labels.  If from a "medium" manufacturer, it gets hard - you have to call to find out their labeling policy.  Jiffy cornbread is not safe, Trader Joe's cornbread is safe, Duncan Hines/Betty Crocker baking mixes are often not safe, Pillsbury is usually safe if the label doesnt include nuts in the allergy disclosure, Trader Joe's "Trader Josef" cake and CHOCOLATE icing are safe but the other cake mixes at Trader Joe's are not. Back To Nature's Granola Classic is the only reasonably priced granola I've found that is safe.  No other flavor of their granola is safe though.
(l) Candy and Gum - I have a list of safe and non-safe.  Skittles, non-chocolate Wonka, Tootsie Rolls, Dum Dum's, Smarties, Hershey's plain Kisses, most Peeps, all Spangler, all Wrigley's are safe.  Bazooka Bubble Gum is not safe (it's made in Mexico and the company cant comment on allergy safety because of that).
(m) Sunflower Butter is safe from the perspective of its ingredients, but then you have to ask about the facility and risk of cross-contamination.

Bubble Gums: Double Bubble (Tootsie) and Hubba Bubba (Wrigley) are safe

Bazooka (by Topps) is not safe - it's made in Mexico and Topps says no cross-contamination info is available.

Bubble Yum (by Hershey's) - pending (customer service closes at 4pm)

Wrigley - Hubba Bubba brand - ALL GUMS made by Wrigley are SAFE, so Hubba Bubba is safe in all flavors and forms (customer services says we can get at Costco but call first to make sure of stock, and also at CVS, Walgreens, Dominicks)

Kraft - Cadbury - Bubblicious - they can't say... you have to read the label and it will disclose any risk of cross-contamination.

Tootsie Roll - Double Bubble - ALL TOOTSIE ROLL PRODUCTS ARE SAFE - they use no peanuts or tree nuts in any product or facility... Double Bubble is widely available (e.g. CVS, Walgreens)

nestle crunch in any size are not safe

hershey plain milk choc kisses are safe