For this child, the initial presentation and evidence for sensitization
against lysozyme, in the context of an egg allergy, are compatible with
the diagnosis of anaphylaxis to lysozyme. Within the hours before the
reaction, he did not ingest any food containing eggs, wheat, fish, or
milk and had a usual meal for dinner two hours before intake of the
drug. When giving this treatment to her son, his mother had no idea that
it could contain egg protein and she did not perceive lysozyme as an
allergenic protein. However, the box mentioned the presence of lysozyme
and also specified ”contains lysozyme extracted from egg”. Previous
reports have described anaphylaxis attributable to lysozyme. One case of
anaphylaxis following the ingestion of Lizipaina® for a mild respiratory
infection was reported for a 15-year-old egg-allergic patient sensitized
to lysozyme4. The SPT was positive for Lizipaina® and
sIgE against lysozyme was detected. Another case of anaphylaxis to
Lizipaina® was described in a 54-year-old patient sensitized to
lysozyme. The SPT was positive for lysozyme (commercial extract) and
sIgE against lysozyme was detected. This patient experienced similar
symptoms 3 to 4 times after the ingestion of cured cheese or raw
egg5. A six-year-old egg-allergic child presented with
anaphylaxis 5 mins after the first use of a deodorant containing
lysozyme hydrochloride, but no lysozyme sensitization was demonstrated,
either by SPT or sIgE measurement6. Other cases of
allergic reactions potentially related to lysozyme were described for
women using vaginal suppositories containing lysozyme, among whom three
were known to be allergic to egg. However, these suppositories contained
other egg proteins, which may have been involved in the occurrence of
the allergic reactions, and none of these patients was sensitized to
lysozyme7. In the child of the case presented here,
symptoms may have been worsened by the presence of a concomitant
infection. Despite the presence of lysozyme in various industrial food
products, our patient may have not been previously exposed because of
his large food restrictions and his aversion to dairy products. It is
also possible that he may simply not have reacted to previous exposure
because the amount of lysozyme contained in food products is too low to
induce an allergic reaction compared to the 20 mg contained in
Lysopaine®.
In summary, lysozyme may induce anaphylaxis in egg-allergic patients,
especially when aggravating factors, such as infection, are present.
Lysozyme can be found in many commonly consumed industrial food and drug
products and its labelling may be misleading, exposing patients to
potentially severe reactions. Indeed, lysozyme is not necessarily
perceived by egg-allergic patients as an allergenic protein. Our
observation highlights the importance of properly educating allergic
patients to recognize allergens, even minor ones.