In T-dependent antigen recognition, the B cell can switch the isotype by first altering the heavy chain gene. This is driven by Tfh cells. The specific cytokine stimulating the class switch determines the isotype of the heavy chain to be synthesized. For your example, interleukin 4 (IL-4) drives the class switch to IgE. You also need a costimulatory signal ...
I am unsure that how much does it answer your question, but have a look at the homepage of DeltaSVM - In his work, Lee et al. have used similar datasets (only for GRCH37 I reckon) and I am sure they will address some of your queries.
As you yourself can better determine which dataset(s) are ones you need.
Because developing a hypersensitivity takes time. If you get exposed to an allergen, the body first has to produce those antibodies that then get used in the hypersensitivity response at the second, or subsequent, exposure.
If you are talking about taking a second test just minutes after the first one, how would your body even "know" that this is a second ...
This answer is based on embryological studies and is limited.
I will extend it later when understand better.
maculae acusticae - walls of utricle and saccule (this most probable area)
cristae acusticae - change in body position
vestibular fibers of cranial nerve VIII (TODO each branchial arch has a nerve - how these differentiate ...