Random lip swelling

Since I was 12, (I'm 40 now) I've had episodes where either I wake up with an itchy lip that then swells up (abroad and at home) or I go out to a restaurant and have a meal and the same again. I've done a full food diary and nothing obvious comes out as an allergen at all. Before it would happen once ever 10 years if that. In the last year it's happened about 8-10 times with varying severity. I am at my wits end as to what it could be. It always starts with a mild itch before my lip just swells up massively. It's always a different area and antihistamines don't really help. I've been taking fexofenadine daily as well after seeing my GP.

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I have no idea what's wrong with me but it's so irritating and the increasing frequency (from once a month to multiple times a week now) is scaring me. Never been allergic to stuff before and now..!