That sensitization to proteins occurs is well established. The only evidence so far produced is that it is the undigested protein that sensitizes and causes symptoms. Frequently, one meets with conditions the symptoms of which would seem to be due to protein sensitization, even though the protein tests are negative. For this reason it seemed to be advisable to try sensitization tests with the decomposition products of proteins in order to determine whether or not they might sensitize and cause anaphylactic symptoms when the whole protein failed to do so. The present work, however, would seem to show that the decomposition products do not sensitize human beings and do not play a part in human anaphylaxis.
We first attempted to digest egg white with normal human duodenal contents in order to simulate as near as possible normal digestion, but this experiment was a failure because of reasons noted below.
WALKER IC, WETMORE AS, ADKINSON J. SENSITIZATION TESTS WITH DIGESTIVE PRODUCTS OF PROTEIN. Arch Intern Med (Chic). 1923;32(3):323-334. doi:10.1001/archinte.1923.00110210012002