I've heard anecdotal evidence that cessation of milk intake can be
followed by a lactase deficiency, which is the root cause of lactose
intolerance.

I have also read that high exposure to any allergen can have the
effect of "sensitizing" those who already have a propensity to
developing a dairy allergy.

Again, lactase deficiency and dairy allergy are separate mechanisms.
It is possible to have one, both, or neither.

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Mark Feblowitz