It's one of those interesting things.

We can discover for ourselves that *our* symptoms are triggered by dairy
(or an specific allergen): my rheumatoid arthritis was triggered by dairy;
my wife's migraines are triggered by sulfites; my son's eczema
is  triggered by several foods. That's not to say that *all* rheumatoid
arthritis is triggered by dairy, that all migraines are triggered by
sulfites, or that all eczema is triggered by food allergies.

So doctors are reasonably reticent to declare these things as universal or
even causal, especially since they're not borne out by research. I
discovered the dairy/RA link for myself. A few years later, controlled
studies confirmed it; we discovered our son's food allergy/eczema link; a
few years later, the very same, very dubious leading pediatric allergist
finally published his supporting findings.

Bottom line: the patient is the best gauge - if it hurts when you do this,
don't do this.

Mark