Is it the same on vacation? I would guess mold. Or dairy. The mucus in stool suggests its diet.

For one of my kids it was laundry detergent, dryer sheets and air freshener. Try to eliminate those and see if it helps. It helped us tremendously. Good luck.

I agree with dairy. My son is like this. And it does not show up on a food allergy test, but it clearly bothers him. It is more like a food intolerance. He does not need an epi pen. Would recommend eliminating it from a diet for a week and then adding it back to see if symptoms go away and return.

ENT and allergist

She is alergic to something obviously. You just haven't been able to name it yet.

Dust allergy?

It sounds like an environmental allergy. Maybe dust mites? Mold? I would have them redo testing. Get someone into your house to do some mold testing and/or get an air purifier/mattress protector.

Food allergy tests are notoriously inaccurate. I get these symptoms from dairy and it has never shown up on an allergy test. It also takes 1-2 days after consuming dairy for the symptoms to appear so if you want to try an elimination diet, I recommend she stay away from dairy for 3-4 weeks to see if it helps. Of course, it could also be a different kind of allergy (or not an allergy at all). If you want to try eliminating dairy, make sure you remove ALL things with milk in them including milk chocolate (a big trigger for me), butter, Cheetos and other junk food with cheese powder on them, and of course all cheese and ice cream. You'll need to check labels carefully and convince her to stay away from pizza. Do not settle for lactose-free items since they still have all the milk protein allergens in them.

My daughter has constant nasal congestion and post nasal drip, despite having deviated septum surgery 2 years ago. That fixed the lack of nasal breathing but she still sneezes constantly, had a ton of postnasal drip and earwax plus complains occasionally about mucus in stool (not all the time though). Weird thing is, she is negative for all allergies and eats pretty healthy and is very active. She also never gets sick otherwise. She notices her symptoms are better when it’s cold outside and they’re definitely worse inside or if the heat is running. She also feels intermittent sinus pressure.

Is this worth digging into more?