From Mad: "Are your allergies all related somehow, do you know? Or is it a combination of independent allergies? Honestly, I don't know that much about how allergies develop or work, so I'd appreciate any info you could give."
A simple description of the allergy process: We have a type of white blood cell that is programmed to recognize the proteins on the outside of cells that constitute "self." If a cell with a foreign protein on its outer membrane invades (bacteria, virus, etc.), those white blood cells recognize "not self" and attack and destroy that cell. There are also specialized white blood cells that remember the protein of that invader, which is what gives us acquired immunity to such things as chicken pox, measles, etc. When it next encounters that protein on an invader, it can attack immediately without have to do any analysis. What happens with an allergy is that those cells recognize something not harmful as an invader and mount an offensive. And having a memory for that "invader" it will continue to happen ad infinitum.
In the case of food allergies, it usually starts with what is called a "leaky gut." Your intestinal linings are made such that protein has to be broken down into smaller molecules before being absorbed through the lining into the blood stream. If you, for a variety of reasons, have a defective lining that will allow whole protein molecules through into the blood stream, then they will be recognized as invaders and allergies result as described above. This description is of a typical "IgE" allergy, IgE being immunoglobulin E, a component of the body's reaction to invader.
Then there are the whole constellation of food intolerances, such as lactose intolerance (intestinal lining does not produce the enzyme to break down the milk sugars), celiac disease (intestinal lining is damaged by the gluten in grains), etc.
Personally, I was born lactose intolerant. Since it was the 1950s, there were not many alternatives for feeding a baby. Today, we have formulas that contain the individual amino acids and broken down sugars for such problems. I was tried on all alternatives to cows milk, and finally my mother gave up and started feeding me solid foods. A baby's intestine is not ready to prevent the absorption of whole protein molecules until a certain age, which is why we don't feed infants solid foods. I imagine that the whole proteins were just flooding into my blood stream, setting up allergies that would bloom over the years. I find it very interesting that I can only tolerate foods that one would initially feed a baby: carrots, squash, rice, beef. Those are all first foods for a baby. Maybe the intestines don't have trouble keeping those proteins out. Who knows.
Interestingly, my sister, who had none of the infant feeding problems that I did, is also very allergic/intolerant to a lot of foods. There is obviously something familial/genetic going on here. The process of natural selection would have knocked us off long ago if not for industrial agriculture
She and I also have developed what one might call "environmental" allergies over the years. Probably because our systems are so besieged by trying to fight off all of the allergens, they have exhausted their ability to deal with fragrances, dyes, artifical colouring, etc. I live a health-food-store life

Natural everything for me, right down to wearing just cotton (not that there is anything natural about the way we grow cotton, but at least it is not directly made from petroleum, just fertilized and pesticided with it!) I have found that formaldehyde plays much the same ubiquitous role in the manufacturing industy that corn does in our food industry. Everything contains formaldehyde, which is my prime environmental allergy: books, makeup, fabric dyes and finishes, building materials, etc. Toxic chemical, many applications, cheap, what could be better for industry and worse for humans, but hey most people will be able to tolerate it without noticing what damage it is doing to them. Sorry about the rant, but I'm as shocked about what I know of formaldehyde as I am about feedlots. Not only that, but "modern medicine" knows nothing of it. I had to put it all together for myself. Helps that I'm an engineer and my sister is a biochemist
So in answer to your question Mad, I am sure that all of my allergies/intolerances are related. There is clearly a genetic component (primary lactose intolerance), a familial component (shared with my sister), and a environmental component (living in a world of products manufactured with toxic chemicals). The interesting thing about all this allergy stuff is that I'm incredibly healthy. I eat an incredibly healthy, nontoxic diet, cannot tolerate caffeine, alcohol, etc., have tons of energy, get lots of exercise. I'll probably live to be 100 like my grandmother! Maybe there is a lesson to be learned here. Maybe my body is forcing me to live like we were meant to, without the petroleum products, manufactured nutrient-free foods, etc. Something to think about.
One more thing. I cannot tolerate the fragrance in most soaps and detergents. They are mostly manufactured from petroleum products. Know what the soap products I use are made from? Yep! - Corn