I found out something important recently: that you can have IgE-mediated allergies to inhalants that don't appear on skin and blood tests. The symptoms are similar to conventional allergies. I've looked into the research on local allergies somewhat, and there's a lot of of research supporting the existence of local allergies, although there's controversy about how common they are.
There's a continuing medical education course online about local allergic rhinitis, which is a local allergy in the nose. The local allergy phenomenon has also been dubbed "entopy" (as opposed to atopy). A review article on local allergies in various organs is ''Entopy': Local Allergy Paradigm by DG Powe et al, 2010. The full text isn't available free online, but it's a good article.
There's "mucosal immunity" in general, immune reactions associated with a particular mucous membrane. Some vaccines are applied to a mucous membrane rather than being injected. For example there's a vaccine being developed for urinary tract infections that's a nasal spray - somehow the immunity is transferred from the mucous membrane in the nose to the mucous membrane in the bladder, and it works better than if the vaccine were injected.
Last I checked, it was uncertain whether local allergies are generated locally, or whether an excessive number of mast cells appear in inflamed tissue, and soak up the IgE in the blood.
The DG Powe article also mentions possible non-IgE mechanisms for local allergies.
Local allergies might be to blame for some delayed food allergies - the kind of thing where you try a food after going on a hypoallergenic elimination diet, and you start feeling bad maybe 1/2 hr to several hours after eating the food, and you stay sick for about 4 days. By "feeling bad" I mean a groggy, sick feeling where one can't think very well.
I have a theory about delayed food allergies: that they're local allergies in the GI tract, and the body tries to prevent the local allergy from becoming a systemic food allergy, because that could be life-threatening. So the idea is that other kinds of antibodies, like IgA and IgG antibodies, come into play to try to prevent a systemic IgE allergy. Allergy shots raise the level of IgG antibodies, and after a while this reduces the IgE level in the blood.
So these other IgG and IgA antibodies, while preventing a systemic food allergy, have vague symptoms like fatigue and difficulty concentrating. The body does something to prevent severe symptoms from these antibodies, so people often don't know they have a delayed food allergy. When someone does a hypoallergenic elimination diet, it changes whatever the body is doing to suppress the symptoms, and then when one tries the food again after the elimination diet, they get obviously sick.
I've read of research supporting local IgE allergies in the gut. The part about the delayed food allergies maybe being in the GI tract in general, including the mouth, comes from an experience I had with sublingual immunotherapy, which means that instead of getting allergy shots, you put the allergens under your tongue. I tried this, I got skin testing for allergies and they made allergy drops to put under my tongue. I was afraid I'd have a reaction similar to my food reactions - I have a lot of delayed food allergies. So I put the drops under my tongue and after a while I washed my mouth out with water very well, so very little of the allergy drops would go down my throat. But, I had a reaction similar to my food reactions, both times I tried the allergy drops. So this made me think I might be having the reaction, partly in my mouth!
Local allergies might explain a lot of things, like some cases of chronic fatigue syndrome, "toxic mold" reactions, etc. Actually there are innate immune reactions to mold, as well as allergies. But if you get skin or blood tests for allergies and the tests are negative, the allergist is likely to say you don't have allergies, even though research shows you can still have allergies.
Doing a hypoallergenic elimination diet and food challenges is about the best way to diagnose delayed food allergies, although the process is full of pitfalls. I've satisfied the diagnostic criteria for chronic fatigue syndrome, because of delayed food allergies. I probably have celiac disease - an autoimmune reaction to gluten grains.
I was sick for 4 years without knowing why, because of a local inhalant allergy. Although I had allergy tests for years that were positive, in the past few years my allergy tests have been negative. My allergy symptoms have always been mostly mental and physical fatigue, not feeling fully awake. I have few specifically nasal symptoms, which made it hard to know what was going on.
When I came down sick 4 years ago, it felt a lot like allergies. It was a chronic bleary state, I felt all the time like I'd just been woken up at 2 am and I wasn't really awake. I went to a couple of allergists, and I was told I should be investigating non-allergy causes. I had had lots of tests for non-allergy causes and they were negative.
Eventually, by a long slow process, I found the cause. Part of it was mold that was getting into my food accidentally. But I was still sick even after I stopped eating the mold. Then I went to stay in a motel, and I found that after 5-6 days I got well! Then I went to the SPCA and I cuddled dogs for 4 hours - and I got quite sick - the chronic bleary state was back again - and I stayed sick for days.
I've had dogs for 17 years, that's how I developed a severe dog allergy. I had a mild dog allergy for years according to skin tests. Now I no longer have allergies at all according to skin/blood tests - but actually, I have a severe dog allergy. I got a lot more sensitive when I started to avoid dog dander.
I'm less sick from the dog allergy these days, with a lot of allergy medications and avoiding dog dander as well as I can while keeping my dog.
I could easily still be very sick, without a lot of persistent experimenting on my own. Sometimes doctors can't figure out health problems for you.
I've read that local allergic rhinitis can be diagnosed at the University of Virginia medical center (in the United States), but most allergists can't diagnose it.