My father also developed allergies in his sixties. And it got worse and worse. Soon he was becoming lactose intolerant as well, and had to start with gluten-free food. He could never be near oranges, unless they were grown without pesticides - the remains on the outside was enough to trigger a reaction. Then he couldn't eat farmed salmon, though he could still eat wild salmon. But there was more and more wild fish he couldn't eat either, which did hurt a fish lover like him. And on and on it went, until he was severely limited to what he could eat and what he could get exposed to.

Then one day he noticed that the mayonnaise he enjoyed every day contained a conservation additive (an E-type, as is how they're labelled in Europe) which he knew he used to have some reaction to in the past, another food product included it and he had avoided that one since like forever. So he quit the mayonnaise when he noticed that. But what happened next was astonishing - all his allergies, lactose intolerance and everything disappeared, and not much later he didn't have any issues with anything.