Over time I learned they are super different, but I am just going to talk a bit about 2 of them. Food allergy & food intolerance.
A food allergy is serious. This means pretty much instantly what you ate will make your mouth swell up, tongue swell, ears swell, throat gets tight, itching, hives, rashes, watery eyes etc. It can range from mild to fatal depending on how much you eat and how allergic you are. These are foods you want to avoid like the plague because it can make you quite ill. A true allergy is instant and requires the presence of Immunoglobin E (IgE) antibodies against the food, and a food intolerance does not
A food intolerance is a delayed reaction & takes place in the gut, causing mostly digestion issues & upset. The classification is a bit more complex.. It can happen in a few different ways.
1. Intolerance can result from the absence of a specific chemical or enzyme needed to digest a food substance. So when you eat the food (say fructose), when the time comes in digestion to be broke down, it won't be able to. This causes a tough digestion & discomfort/pain. Often this is called a hereditary intolerance
2. Intolerance can be a result of an abnormality in the body's ability to absorb certain nutrients needed. (Malabsorption)
3. Intolerance can also be a reaction to naturally occurring chemicals in foods. So it might not always be item X itself causing issues, but a component of it. An example of this is salicylate sensitivity. This means all foods containing that chemical will give you a reaction.
An intolerance is delayed. Often times it can happen 1-2 days AFTER you ate the offending food. Therefore it's hard to figure out the culprit by looking back at what you ate. Some happen 12 hours later, some 6, some 36. That part gets a bit confusing.
The food allergy testing is most commonly done by blood test checking for iGe antibodies to certain foods. This is important to know if you have a life threatening allergy to anything.
A food intolerance test is called MRT testing & it's incredibly sensitive and accurate. Also a blood test. You want to avoid the foods that are an intolerance if you have stomach troubles. Especially if you have leaky gut or are on lots of antibiotics which compromise the gut lining & good bacteria. An intolerance isn't life threatening but it can be painful & really damaging to the stomach & intestines. I REALLY recommend this to those with Lyme. Going on a gluten free vegan diet will help, but until you remove foods not tolerated by your stomach you won't be able to fully help your immune system to the best of your ability (80% of your immune system is in the gut). And we all know you need the strongest immune system you can get to fight Lyme!
I had the MRT testing done in 2010 and I had A LOT of foods I ate commonly come up. It made sense because I had a horrible case of leaky gut & candida. Not a good situation in the ole stomach. Of course I was stubborn I will be honest it took me about a year to cut those foods out & work on healing my stomach. But since the end of 2011 I have gone on a strict diet, took care of the candida, added in lots of probiotics, I drink marshmallow root tea daily & take DGL licorice. I got serious about things basically. And as you can see below (I attached a photo), my intolerance list is much smaller. A lot of things have moved off of it & some others moved on.
In order to better help my stomach out I now know what I can add back in & what foods I need to take out to continue to heal. It's not sure why these intolerances change in time, or why some new ones develop to other foods. I also did an iGe test to see how that's "changed" and I'm waiting on those results still.
This came down to me just wanting to better help my stomach out, since its constantly giving me pain & trouble. Also, with Lyme for some reason you develop a lot of different allergies.. It's very odd. I have a soy allergy but I also developed an apple, pear, kiwi, cherry allergy. My whole mouth swells up & it's actually really scary! A lot of times I will eat something and get an itchy mouth & stop without knowing what did it. So for my safety & to spare myself we did that testing as well.
This was long but I hope it helped better explain the two!