Allergy to honey and royal jelly: a case report

Honey is a complex mixture of different components derived from bee’s gland secretions, flower nectars and pollens[1]. Honey allergy is very rare but can lead to serious clinical manifestations, such as anaphylaxis. On the other hand, the royal jelly (RJ) allergy is more frequent and has been widely investigated[2]. The main proteins of honey and RJ belong to the family of Major Royal Jelly Protein (MRJPs). Amongst them, MRJP1 and MRJP2 are the main allergens identified in the RJ. In this study we describe the case of an allergic reaction occurred in a 21-year-old girl immediately after the honey intake. This product had been consumed previously without any clinical symptom. In order to identify at molecular level the patient's sensitization pattern, different experimental and clinical tests were performed. Prick to prick test was performed using six different types of honey and two samples of RJ obtained from different producers. The patient resulted positive to all samples. Samples of orange and wildflower honeys and two samples of RJ were characterized for: 1) their protein profile, by electrophoretic techniques; and 2) their antigenic properties by immunoblotting, where the patient's serum was used. The electrophoretic analysis showed that the most abundant proteins in honey and RJ had a molecular weight (MW) of 64.2 kDa and 60.4 kDa, respectively. The same proteins showed the highest immunoreactivity versus the patient's circulating IgEs. In orange honey three further proteins, having molecular weight of 126 kDa, 109 kDa and 53.2 kDa were recognized by serum IgEs, while in RJ only a further protein with MW of 51.3 kDa showed immunoreactivity. According to the scientific literature (MW close to 60 kDa and relative protein distribution), the most abundant protein in honey and RJ samples was identified as the MRJP1. Similarly, the proteins having MW close to 52 kDa were identified as MRJP2. Even though the allergy to honey is usually associated with Asteraceae pollen or to bee venom, this was the first clinical case described in Italy due to proteins from bee’s gland secretions.