I'm glad you were able to be seen again quickly. As to "hoping it really is that simple"... managing food allergies can be challenging and there is no one and done fix. If it's an ingestion reaction it's important to figure out what's causing it and avoid the allergen. Food allergies can be dangerous and reactions aren't predictable. It's important for you to get a proper diagnosis and a treatment plan from an allergist.
Normally, an ingestion reaction will start within minutes of eating, but can take up to 4 hours to manifest. The symptoms can linger for a few days afterward. Do you have any idea what you had to eat and drink in the hours leading up to your hives?
There are also hives which can be caused in response to a virus. Is it possible you were slightly ill (the nausea and bloating) from a virus and this is the result? That would be simple. Uncomfortable until they go away, but simple in that you don't have to actively do anything to prevent it (or worse) from happening again.
TX - USA
DS - peanut, tree nut, milk, eggs, corn, soy, several meds, many environmentals. Finally back on Xolair!
DD - mystery anaphylaxis, shellfish.
DH - banana/avocado, aspirin. Asthma.
Me - peanut, tree nut, shellfish, banana/avocado/latex, some meds.