Exercise-induced (EI) hypersensitivity disorders contain EI-asthma, EI-bronchoconstriction, EI-rhinitis, EI-anaphylaxis and EI–urticaria. They can occur in both recretional athletes and elete athletes as mentioned in the question. The reasons for EI hypersensitivity contain
airway dehydration (risk for EI-asthma and EI-rhinitis),
increasing exposure to pollutants in air (risk for EI-asthma and EI-rhinitis),
exercising too early after food (such as wheat and shrimp IgE sensitivity causing anaphylaxis) and
urticaria with unusual temperature change such as elevated temperature in endurance atheletes. The last can be associated with things such as whear, blisters and anaphylaxis.
This is to some extent discussed on pages 959-960 in Exercise-induced hypersensitivity syndromes in recreationaland competitive athletes: a PRACTALL consensus report (what the general practitioner should know about sports and allergy).
Why increasing prevalence?
Environemntal factors such as pollution could be a factor for the increase.
Elite atheletism has developed over years to distributions having flatter tails: only minority get the rewards and can maintain their career and health.
Technological development such as IgE microship inference testing
Better knowledge such as improved classification of urticaria with different classifiers such as tryptophan
EI-urticaria and associated anaphylaxis
There are many different types of urticaria such as immunoglobulin-dependent urticaria (mostly IgE), physical urticaria (cold urticaria, solar urticaria) and complement-mediated urticaria (such as heat-urticaria, serum sickness). Other possible pathogenetic mechanisms are in Table 3.2 of the book Urticaria
by Beate M. Czarnetzki, 2012.
There are many meditators to urticaria such as histamine, probably the most researhed so far. Histamine leaves marks of urticaria on the skin with the following ways: initial red mucula, then surrounding erythema and edema last (skin ballooning, filled with fuild). This is commonly associated with burning pain and itching. More in 2.3.1 of the book.
"Histamine does not readily cross the blood-brain barrier" (2.3.1 Section in the book). According to animal tests, injections of histamine into the ventricle can cause symptoms such as increased blood pressure, hypothermia, prolactin secrecation and increased adrenocorticotrophin by the book. Histamine has high concentration in particularly hypothalasmus. Neurons have H1 and H2 receptors and histamine acts as neurontransmitter.
Serotonin is other mediator besides the histamine. There are differences such as vasocontriction but also similarities such as that both serotonin and histamine can be increased with estrogen. Both serotonin and histamine can be considered as inflammatory mediators:
"[serotonin] is considered to be an inflammatory mediator, along with histamine. Edema, bronchoconstriction, immunosuppression, and joint swelling are produced by the release of serotonin from platelets or other cells. As inflammatory mediators, serotonin and histamine are directly involved in asthma, hives, gastrointestinal damage from alcohol, nerve cell damage, edema, and shock." (Web article here).
The drugs used to treat the inflamation contain anti-histamines (probably most popular nowadays) and anti-serotonins.
When the body recovers from food-induced inflammation such as beans rich in estrogen, too early physical exercise can cause anaphylaxis and urticaria signaling to stop augmenting the inflammation. So a mechanism for EI-hypersensitivity is an imbalance in neurotransmitters (serotin and histamine) that is caused here by estrogen-rich foods. In order to avoid shocks again, it is important to analyse the whole diet over past 24 hours.
EI-asthma and EI-rhinitis
The author has not yet investigated the topic.
The increasing prevalence in allergies and poly-sensitivity seem to be due to multiple factors such as pollution, other environmentaral reasons, food supply and more athletic demand. There are also causes to which athletes can affect such as proper hydration and lack of rest. Certain symptoms such as EI-urticaria and EI-anaphylasis require closer attention to diet such as knowing precisely the diet over the last 24 hours before the shock to understand it better and ensure healthy athletic participation in the future.
A comparison between recreational athletes and elite athletes is in the publication "Exercise-induced hypersensitivity syndromes in recreational and competitive athlete" that was discussed to some extent in the answer above.