Too much salt in the diet can be a problem, of course, but it also matters what kind of salt you're taking in. You can't live without salt entirely, so I doubt very much if it's an actual "salt" allergy.
Most commercially prepared foods use the cheap stuff that has added anti-caking agents in it. And, that "no salt" is the worst, because that's simply purse MSG. As a migraine sufferer, I know all about MSG. This is why I have to avoid commercially prepared foods, especially restaurant foods. Certain types of restaurant fare notoriously use MSG in their cooking, because it works as a meat tenderizing agent. This is unfortunate that some types of cuisine are known to have MSG in them, unless the restaurant signs declare that they're not using MSG.
However, some of the various cooking sauces could have MSG or other types of preservatives, so declaring that they don't purposely use MSG doesn't mean that their foods are completely MSG free or sulfite free.
I strongly suggest avoiding all commercially prepared foods, including the packaged processed foods that most people buy for convenience. While you're at it, I would avoid anything with cornmeal in it, because the very process of making corn into cornmeal that is typically used commercially is full of sulfites. So, no tortilla chips either--even if you buy the slightly better for you kind sold at natural food places or Trader Joe's that say they use sea salt.
If you're NOT allergic to corn itself, you would be better off getting an air popper. The popcorn is better for your health, just as fast to make, less potential of burning than microwave popcorn, doesn't have all those unpronounceable chemicals in it and doesn't have the usual table salt in it. DO NOT use table salt while you are figuring out what the problem is, because that anti-caking agent is a sulfite agent. You can try eating the popcorn plain with no oil and salt for now, 'til you've had a chance to heal. Later, you can buy UNsalted real butter to try on your popcorn, or you can see how you like a light touch or extra virgin olive oil or other types of healthy oils. Go without salt for a while longer. Then, when you are healed, you can try a good quality sea salt. I would suggest the red sea salt that you can buy fairly inexpensively in bulk. You will be able to buy just a little bit to see how you do with that as well.
A good alternative to french fries is buying your own fresh potatoes. Simply cut them any shape you like, toss with light olive oil (since you're cooking with it, don't use the extra virgin unless that's all you have--you lose the potential health benefits from heating the oil). Then, spread out on a baking sheet and bake at 350 degrees 'til they are done. They can be as brown as you want. Check every few minutes and remove the ones that are more done as you go, so you don't burn any. Burnt tastes so bad and is a real turn off. You can either add a bit of the red sea salt (go very easy with it) before or after you bake the potatoes. You can try this without salt for when you're missing french fries and can't tolerate the burn from any salt touching your mouth.
Look for foods that have natural sodium content in them, like celery. You can't live without salt entirely. Celery is an allergy for me, so I can't use it myself, but there are other foods with natural sodium content in them. So, try an online research to find out which foods have this. It will help you get some sodium without irritating your mouth while it is healing.
Bottom line: You're going to need to learn to cook your favorites yourself. You must avoid weird chemicals you can't pronounce. And, you definitely must avoid MSG and sulfites. Salad bars are notorious for having sulfites in their fresh vegetables, so no salad bars. Back to making your own there, too.
Hope these suggestions help. I have to do these things myself, since I suffer migraines. So, my allergic reactions present themselves differently than yours do. But, I have had mild mouth irritations in the past before I figured out what the problem was. No movie theater popcorn, as delicious as that is. I can't even have corn at all, or I will get a horiffic migraine. So, you're fortunate if you can still have air popped popcorn.
Hi Im Denica Im 25, I just wanted to say thanks for writing about ur situation and helping me not to feel something is wrong with me and Im alone in this situation, I have all the same Symptoms as u mentioned I even have problems if I go to the beach and the water is to salty. Its very frustrating cause I cant eat some of the foods I really enjoy like salted pistachios without having to put it directly into my mouth making sure it doesn't t touch my lips . I have been searching the Internet for some kind of remedy to help with the situation but to no avail since . Just wanted to say thanks for helping making me not feel weird and alone . By the way mine started in my twenties as well.