I discovered I was intolerant to garlic just before going to Italy. It was shockingly easy to accommodate that intolerance, there! Red sauces seem to be more likely to be full of garlic.

Research low FODMAP options. It's much more restrictive, but keeps out onions and garlic. I've found that keeping things simple: ordering a meat, veggies, and potatoes makes it easier to tell the wait staff about the allergy and they may be able to accommodate. As weird as it sounds, you are probably fine at true Italian restaurants. Look at the menu and don't assume everything contains garlic (but definitely give them a call or talk to the waiter). Stuff like carbonara shouldn't. When I was doing low FODMAP I ordered steak frites everywhere and made sure they didn't use anything except salt and pepper on the steak. Expensive, but delicious.