Lactose issues are fascinating. Some peop’e are triggered by pasturized milk, others can't handle milk at all. Some people can only handle cooked milk, others cheese until limits. For some lactose works, and for others not - to the point of upsetting stomachs. There's even compelling annecdotes (to my knowledge, no research) indicating that adding a couple of drops of any citrus to milk helps some people.

For some reason this all blows my mind.