I will now tell you what I would have done if I was in your shoes.
I see you have done a lot without getting results, so you should now maybe try to do it the other way around.
Instead of eliminating one or 2 or 3 things from your diet at a time, eliminate everything for a short time, and look for results.
When it comes to allergies or intollerance, (and we know allergies can be behind the EC cause there are people who cured EC by eliminating one or several allergens), there are so manyy things people can be allergic to, that trying it one by one, or 2 by 2 or 8 by 8 would take very ong time.
The better approach is to eliminate everything, and if that works, include things one by one, or 2 by 2.
Let us now forcus on food first.
Majority of those cured achieve cure by eliminating something from their diet, so it is reasonable to test the DIET HYOPTHESIS first.
I am not saying it is 100% that diet is your problem, but if diet is problem for 80% of people with EC, I would first test the DIET HYPOTHESIS.
What is the DIET HYPOTHESIS?
The DIET HYPOTHESIS says: "There is something in your diet causing peeling lips"
How to test it?
By elimination. You already tested gluten, milk and sugar.
But, there is a faster way.
The fastest test is to eliminate everything.
Not the most convenient test, but the fastest. You just drink water for several days, and you take magnesium to flush your intestines clean.
If the diet is your problem, your lips will be cured in 3-5 days of Water Fasting (+ clean intestines).
Intestines can be cleaned by enema, or colonics, if you don't like the taste of magnesium sulfate or magnesium chloride.
As I said, this is the fastest way to test the diet hypothesis, but not the most convenient.
The problem with this test is that you will be hungry, the first 2 days, and quite many people are not used to hunger, so they quit on the day 1 or day 2. Check the Water Fasting forum on CureZone. every second faster gives up to hunger within the first 2 days.
The much more convenient way to fast is vegetable juice fasting.
You focus on just very few vegetables (like carrot, cabbage, beetroot), and you make sure you have a bottle of fresh juce with you wherever you go during a day.
Any time you are hungry, you just drink the juice.
Carrots have a lot of Sugar so you will not be hungry.
The main advantage is there is no hunger, and you don't need to drink water. If there is something in water you react to, that will be eliminated too.
The main disadvantage is:
What if you include in your juices something you are intollerant of?
There are people intollerant to carrots.
For example, many people have problems with lemons and oranges, so I would definitively eliminate all citric fruits.
The another disadvantage of juice fasting: you need to invest money in some juicer.
Now, juicers are not very expensive, for about $100 you can get a decent centrifugal juicer in your local store or on Amazon.com or on eBay.
For more money you can get a screw juicer that will last 10 or 20 years.
I have one Green Power double screw juicer I purchased 17 years ago, and the juicer still works today.
But, a cheap centrifugal is more than enough, if all you want is just to test the diet hypothesis (up to 7 or maybe max 10 days of fasting, if you get positive results the first 3-4 days).
Magnesium or enema to flush intestines is advised, to make sure you are clean from inside.
Anything you carry in your intestines will spoil results, and you have just wasted several days of juicing.
Colonics are also advised, if available.
If your lips improve 10 - 20% within the first 3- 4 days of fasting, the hypothesis is most likely true, so you can continue fasting until the lips are 100% cured.
The rest of your life :) you can use to figure out what it is in your diet you react to.
After juice fasting, or after water fasting, if you include in your diet one or few things per day, you will pinpoint the problematic foods.
The first food that gives you burned or dried lips is to be blacklisted.
After awhile, you will have a decent blacklist, and as long as you stay away from those foods or drinks, your lips will be like new.
What if you don't get any improwement (not even 5%) after the first 3- 4 days of fasting?
In that case, my guess is: The diet hypothesis may be wrong. There could be something else causing the condition.
I would eliminate every single cosmetic product, soap, anything.
It could be water. There are people who react on chlorine or fluoride in water.
Do not shower for several days while fasting, to also eliminate that possibility.
If that doesn't help, it could be a dental problem.
Learn about Amalgam , root canals , cavitations .
Do you still have your molar teeth?
Do you have any dental fyllings ?
A dental panoramic scan can revceal a lot.
It costs money, as dentists are not cheap.
If the problem is not dental, it could be something in your house.
Allergy to wall paint?
Fire retardants in your furniture?
Insecticides used by previous owner? People sometimes poison the whole house trying to exterminate ants or roaches.
Was house or basement damaged by water? Learn about black mold, black fungi. It can make people sick.
Any extra radiation?
Mobile phone mast on the roof of your building?
To thest the house hypothesis, you should go camping for 7 - 10 days.
If no improvement on your lips, it is not your house.
If there is some improvement, it could be the house.
And so on.
Test each and every possible hypothesis, until you find the answer.