I have a mild allergy to dairy, citrus & yeast. I can tolerate some dairy if processed/low fat (a full fat flat white is too much milk, but a skim flat white is ok), I don't generally eat lots of bread or citrus & do ok.
I have recently had much worse hay fever than in past years & i noticed that when we were away at the beach DH & Ds2's hayfever was much better, but mine was far worse... so I looked at what I'd been eating & noticed that while we were on Holidays I'd had bread 2-3 times/day + pizza = lots of yeast. So I basically cut out all yeast apart from the occasional glass of wine (yeast is in wine) & the odd meal that has breadcrumbs in it... I haven't needed antihistamines for a few weeks EXCEPT last Thursday when in a rush to get to a meeting & missed dinner, so I grabbed the left over "pizzas" made on English muffins to eat in the car... that night I suffered.
For me bottom line is I'm probably better off with no dairy, yeast & citrus, but regular small amounts are ok, but if I have a large amount after having none, I suffer...I am still going no yeast because it cuts out lots of carbs & helping with losing a few pesky Kg's, but I when I go back on it will be limited to 1 slice of bread/day.