Allergy to avian egg

To the Editor:

I read the article titled “Quail egg allergy with tolerance to chicken egg: A case report” by Delgado-Prada et al with great interest.¹ However, clarification of my questions about this case report would help us better understand the case and this fascinating topic.

Although similar case reports have been published previously,^2,3 Delgado-Prada et al¹ have presented clinically significant cases. Here, a case of a child who has quail egg allergy but is tolerant of chicken eggs is described.¹ Another case of a 10.5-year-old girl without chicken egg allergy who experienced an anaphylactic reaction after consuming raw quail eggs has also been reported.² In a child with tolerance to chicken eggs, severe non–IgE-mediated enterocolitis associated with quail eggs was observed. Similarly, IgE-mediated allergy to duck and goose eggs has also been reported. Ovalbumin has been identified as the protein responsible for this.³

There is confusion regarding whether all or some of the other bird eggs, which are thought to be cross-reactive, should be eliminated from the diet of patients with chicken or quail egg allergy. In patients with chicken or quail egg allergy, it is generally recommended that other bird eggs, which are more common, also be eliminated from the diet; however, it is thought that some patients who tolerate these eggs may be able to consume them.⁴ These and similar cases demonstrate that this general approach is incorrect and that individualized adjustments are essential.

One study found that the rate of sensitivity to other bird eggs in patients with chicken egg allergy was 96.1%.⁵ However, the most common sensitivity was found to be to quail eggs (at a rate of 69.2%) and duck eggs at a rate of 65.5%.⁵ The case presented in the article by Delgado-Prada et al¹ is vital in helping to clarify this situation.

The case report by Delgado-Prada et al¹ contains several significant findings that surprised us, including mild-to-moderate black bands with a molecular weight of 37 to 50 kDa in the patient's IgE Western blots for duck and goose. However, the bands appearing between 7 and 12 bands were not very dark.¹ Delgado-Prada et al¹ state that “the immunoblot revealed a protein band in quail, duck, and goose eggs.” This result also suggests that the patient may cross-react with goose, duck, and quail eggs, rather than with chicken eggs.¹ However, no skin prick tests, serum-specific IgE tests, or oral food provocation tests were performed in this patient. In fact, this should have been clarified beforehand, when adjusting the patient's diet.

I agree with the view expressed by Delgado-Prada et al¹ that this case highlights the complexity of egg allergies and emphasizes that serologic cross-reactivity does not always translate into clinical symptoms.¹

In conclusion, I would like to thank Delgado-Prada et al¹ for this beautiful and high-quality case report and its results, which have increased our knowledge and awareness about allergies to avian eggs other than chicken and quail eggs.

Disclosure statement

Disclosure of potential conflict of interest: The authors declare that they have no relevant conflicts of interest.