Alright, I'm going to dump/vent. I've had food allergies since kindergarten. Out of college I got a job that immediately required travel after training commenced.
As in, leave the house at 3:30AM for the airport monday morning and get back 10PM-midnight on Thursday night travel, and stay in hotels in the interim. (2016 dropped off on the travel but the experience remains...)
I will say this: Travel, logistically, is a nightmare for allergies. I am allergic to eggs and seafood. Airports traditionally have small kitchens. Shrimp or fish & chips will generally rule out anything fried/on a grill, while egg will generally rule out frying (breading) or griddles due to breakfast prep. Airports are probably the worst culprits depending on allergies because due to staff/small kitchens and shared cooking surfaces in a small place they generally don't have much care or reason to be careful. (If you are traveling regularly though, you can make something work. I got the same antipasto salad from the same bar in Chicago essentially every week. The staff would see me so much they would just pour a Sam Adams and order the salad on my pass through on Thursdays...)
Domestically, it's easier, at least in the sense of pre-packaged food (pack your bag with it and pop it open if you're hungry). It's not necessarily the "healthiest" option but it suffices for keeping sated during transit. International is tough as food is generally required to be declared/secondary inspected. Most of my work brings me between US/Canada which means customs on either side, so I avoid traveling with anything other than food/gum to avoid hassle with Global Entry/NEXUS (trusted traveler programs for expedited customs clearance).
I'm less afraid of my allergies than I used to be. My first business trip resulted in a cross contamination issue that almost resulted in ER/ambulance (throat swelled almost completely shut) which was a valuable experience on keeping an autoinjector and antihistamines on my person, knowing where the nearest hospital was, and knowing how to interpret whether I was getting a handwave on allergies or honestly cautioned/interpreted. I have cousins who have allergies and are deathly afraid of eating out and of the sight of peanuts, but recognize due to dust how that is a different allergy from others.
My main advice knowing people with allergies is to be mindful, be alert (e.g. always inspect what you're eating), and always carry epinephrine auto-injectors on your person. I have had coworkers who just leave them in the trunk in the winter/summer and beyond accessibility I tell them about the tolerance of the medication and it's not suited for this, plus need to access the medication.
If anyone wants advice on travel, the general advice would be to be careful generally, and most restaurants at your destination will be understanding equally as to whether you are a local (ignorant to kindhearted but wrong to actually careful). In-transit, airlines are generally careful on the snack front (although not on cleaning tray tables/interior) and airports are the worst.
If seeking specific advice beyond the above for travel, please direct message me on this forum.
I promised to vent at the start of this post and here it is: If you see tablets everywhere (every seat) at a restaurant at an airport, run and don't look back. It's run by a company called OTG and they suck. Food is not only way overpriced but ordering through a tablet reduces the human factor in explaining an allergy. If you explain an allergy they still mess it up. It's all well intentioned but menus are limited and allergy understanding/staff communication is really hampered. The biggest issue is if you are at at a location where OTG serves the terminal exclusively. If you fly United out of Newark [EWR] (not United Express) then my recommendation would be to solely drink, buy pre-pack at the convenience store, or pack your own food as appropriate.
My blessing was getting to regular locations, as I was able to establish regular dishes and handling routines on an ongoing basis. There are some dishes I deeply miss as I am no longer visiting those areas, but such is the pain/luxury of a regular area for business travel...