There is an observed correlation (not causation, btw) between adult-onset food allergy and proton-pump inhibition-- but that is definitely NOT the same thing as the hash of stuff in that first post.

The above post is not at all in line with generally accepted guidance or best practices regarding IgE-mediated food allergy or hypersensitivity.  The person who posted it is very likely a forum troll trying out the system here.   

Beyond that, I think that this sums it up rather nicely, in fact:

pH Quackery and proton Homeostasis

Food allergies is what results, when your Immune system is inappropriately activated.  Your Immune system, is  designed to attack Bacteria, Viruses and Parasites.  It is not intended to attack the nutrients consumed, but this is exactly what happens, when pathogens are allowed to enter the digestive tract.
When the immune system is activated, antibodies (also called Immunoglobulin) are produced.  Antibodies, in turn trigger an inflammatory response.  Inflammation, causes pain and tissue damage, leading to further symptoms.  Increased mucus production is also caused by Allergens, entering the digestive tract.
There are two types of antibodies produced, IgE and IgG ,by the immune system, in response to allergic reaction to foods.  The IgE reactions typically occur immediately after the Allergen enters the small bowel. This reaction, in some cases, causes serious health problems.  Some of the reactions are; swelling of the lips, tongue, throat, hives, bloating, abdominal pain, vomiting, nausea and sudden diarrhea. IgE reactions can also lead to many other symptoms, not generally recognized as being caused by food allergens.
Many food allergies, are not IgE reactions, but IgG reactions, which usually show up hours, or even days, after the allergen enter the small bowel. IgG reactions usually result in constipation and/or diarrhea, bloating, gas, and abdominal discomfort. The IgG reaction can also cause drowsiness, or a tired feeling, after eating.
In many instances, food allergies are the result of incomplete sterilization and conversion, of proteins that are consumed.  Many proteins are Allergens and will cause allergic reactions, if they are not broken down and sterilized, before entering the small bowel.  When proteins enter the stomach, they are broken down and sterilized by strong Hydrochloric acid, produced by the stomach's parietal cells.  The proteins are converted into Peptides, by the action of the peptic enzymes. These two elements (hydrochloric acid and pepsin), are responsible for the elimination of many allergens, pathogens and bacteria in the nutrients consumed.
The peptic enzymes, are most active in the conversion of proteins, when the pH of the Hydrochloric acid is at 1.0 to 2.0 pH.  When the strength of the acid drops, the peptic enzymes become less active, in the conversion of proteins.  At pH 5.0, the peptic enzymes are no longer active, in the conversion of proteins and there is reduced sterilization, of the nutrients. At 5.0 pH, raw unsterilized and unconverted nutrients are dumped into the small bowel, resulting in allergic reactions.  There is no diagnostic test, or skin allergy test, to determine if the proteins consumed are being properly sterilized and converted.  The reduction in the strength of the Hydrochloric acid is called Hypochlorhydria, in extreme cases it is called Achlorhydria.
Hypochlorhydria can occur at any age, but it usually occurs in the 45 and up age groups. In many cases, as a person ages, the parietal cells wane in their ability to produce strong enough acid. In addition to aging, hydrochloric acid production is  inhibited by the use of various medications, such as antibiotics, antihistamines and especially Proton Pump Inhibitors. (PPIs).
Reduction in the strength of the stomach acid, is responsible for people developing food allergies that they never had at a younger age. Everyone that has food allergies should get a pH diagnostic test. A pH diagnostic test will allow a doctor to accurately determine the quantity and type of medication, necessary to correct the unbalance condition, in the digestive tract.  For more information search the web for pH diagnostic test, pH capsule test, or pH gastrogram