A rare case report of rosemary-induced anaphylaxis

Introduction

Although rare, allergy to aromatic herbs commonly used in cuisine, cosmetics, and homeopathic medicines is being increasingly reported [1]. Rosmarinus officinalis, commonly known as rosemary, is a plant native of the Mediterranean region, widely used across the globe as a spice, flavoring agent, preservative, and for medicinal and cosmetic purposes [2]. It is a member of the Lamiaceae family, the most popular plant family in Southern Europe and Mediterranean cuisine, which also includes basil, oregano, lavender, thyme, and mint [1]. While definite incidence of allergic reactions to aromatic herbs is not well established, it is likely underestimated as the diagnosis involves a high index of suspicion [1]. Clinical manifestations may vary from isolated mucocutaneous involvement such as allergic contact dermatitis, the most commonly reported adverse reaction, to life-threatening events, such as asthma exacerbation or anaphylaxis [3]. There have been isolated reports of allergic reactions to aromatic herbs such as mint, thyme, and lavender, mostly in adults [4–7]. In the particular case of rosemary, unlike allergic contact dermatitis, food allergy and systemic reactions such as anaphylaxis have not been described [2, 8, 9].

Case report

A 16-year-old female with morbid obesity and insulin resistance treated with metformin was admitted to the Pediatric Emergency Room (ER) with a disperse pruritic maculopapular rash of unknown origin. She had no fever or additional symptoms. Ingestion of new foods or medicines, changes of perfumes, detergents or face and body lotions, and insect stings were denied. Additionally, she had no known allergies to date. The patient had a family history of asthma (first-degree cousin). Physical examination was unremarkable except for the aforementioned rash and she was discharged with oral antihistamine. Five days later, due to rash progression and worsening of pruritus, she was reassessed and medicated with benzyl benzoate (Acarilbial^®) due to probable scabies. About one hour after topical application, the patient was readmitted to the ER presenting with respiratory distress, itching and lip edema, nausea, and tachycardia. Immediate administration of intramuscular adrenaline, intravenous hydrocortisone, and intravenous clemastine led to complete remission of symptoms. Serum tryptase levels were not determined due to their unavailability at the healthcare facility in an emergency context. Considering the anaphylaxis diagnosis, she was prescribed an adrenaline autoinjector and was referred for further consultation.
On later evaluation, the patient reported seasonal nasal symptoms, and stated that 2 h prior to the first allergic reaction (urticarial rash) she had a meal with tomato sauce and aromatic herbs, including rosemary, which she claimed to have never eaten before. Serum basal tryptase levels were within normal limits (5 ng/ml). Skin prick tests with commercial extracts of aeroallergens, latex and some food allergens were performed and were positive only for Dermatophagoides pteronyssinus (5 mm wheal). Prick-to-prick skin tests with rosemary (6 mm wheal) and lavender (Lavandula angustifolia and Lavandula latifolia, 5 mm wheal each) leaves, another member of the Lamiaceae family, were also positive. Due to the unavailability of isolated benzyl benzoate (without excipients), an open controlled application testing with Acarilbial^® (benzyl benzoate plus excipients, namely rosemary oil) was posteriorly performed, yielding a positive reaction. Given the recent episode of a sudden onset multisystem clinical reaction presumably related to rosemary mucocutaneous contact, an oral food challenge was not conducted. Considering these results, the patient was advised to avoid both ingestion and skin contact with rosemary.
About six months later, she was admitted to the ER with a new episode of anaphylaxis immediately after eating potato fries seasoned with rosemary. Later that same month, she experienced two additional anaphylactic reactions, one after touching a rosemary bush and another after only passing by the same bush on her way to school. Complete remission of symptoms occurred after intramuscular adrenaline administration in all admissions. Prior to discharge in all three admissions, the importance of avoiding rosemary herbs and plants and rosemary-containing products was reinforced.

Discussion

To our knowledge, the presented case report describes the first known case of rosemary-induced anaphylaxis in a pediatric patient. Rosmarinus officinalis, similarly to other aromatic herbs widely used in various contexts, is infrequently, albeit increasingly, acknowledged as an allergenic substance. As additional clinical reports demonstrate, sensitization to aromatic herbs, including rosemary, is an emerging concern in the field of allergology, and most frequently presents with isolated mucocutaneous involvement, such as allergic contact dermatitis [3, 8, 9]. However, it can also present with severe and potentially life-threatening systemic reactions such as anaphylaxis, as shown in this case report [4–7].
This clinical case underscores the challenge in identifying the specific allergen responsible for an allergic reaction. The vague nature of the initial symptoms, a disperse pruritic rash with no identifiable trigger, hindered the immediate suspicion of an allergic etiology. As the case unfolded, a temporal association between the patient’s allergic manifestations and rosemary exposure was established, prompting a more comprehensive investigation. This investigation included skin prick tests, as well as an open controlled application testing with Acarilbial^®, a pharmaceutical product that contains rosemary oil in its composition. These diagnostic tools were instrumental in confirming the link between the patient’s symptoms and rosemary exposure. It is worth mentioning that an oral food challenge was postponed as the occurrence of anaphylactic reactions subsequent to rosemary exposure contraindicated its execution.
This case report also highlights the potential for severe systemic reactions following ingestion, inhalation, or skin contact with one allergen, illustrating the comprehensive impact of allergen sensitization. It also underscores the importance of complete avoidance strategies, including dietary restrictions, avoidance of skin contact with rosemary-containing products, and minimizing exposure to the herb in its natural form.
Anaphylaxis is a severe form of allergic disease and recognizing the causal agent is essential in preventing recurrences. Despite counseling about the importance of avoidance measures, the patient experienced subsequent anaphylactic reactions after supposedly accidental exposures to rosemary, emphasizing the need for strict adherence to the aforementioned avoidance strategies. The prompt administration of intramuscular adrenaline during each episode effectively resolved the symptoms, emphasizing the importance of the prescription and education on proper use of an adrenaline autoinjector for immediate self-administration.
It is noteworthy to mention that the unavailability of isolated benzyl benzoate for testing was a limitation in the investigation process of this patient, as this drug itself can trigger anaphylaxis [10]. The inability to measure serum tryptase levels during the initial emergency presentation can also be considered a limitation; however, normal basal serum tryptase levels ruled out mast cell activation syndrome. Furthermore, the positive skin prick tests with rosemary and lavender, both members of the Lamiaceae family, offered valuable insights into the potential cross-reactivity within this plant family. This consideration is important when managing and advising the patient to avoid allergens related to the same botanical family.
In light of the comprehensive discussion on the challenges presented by this clinical case, it is pertinent to explore the potential role of the patient’s obesity in her allergic manifestations. Obesity is increasingly recognized as a significant contributor to the severity of allergic reactions. The pro-inflammatory immunological effects of adipose tissue may exacerbate immune dysregulation, thereby increasing the risk of food allergies and heightened allergic responses [11, 12]. Furthermore, gut microbiome imbalance induced by obesity may further enhance susceptibility to food allergies, asthma, or atopic eczema [11, 13]. This case report may serve as a poignant example of the intricate interplay between obesity and allergic conditions, underscoring the need for further research to elucidate the underlying mechanisms and develop targeted interventions for individuals with obesity-related allergic conditions.

Conclusions

This patient report highlights the importance of considering more uncommon allergens, such as aromatic herbs like rosemary, as triggers for severe systemic allergic reactions. A thorough evaluation, including detailed patient history and comprehensive allergy testing, is the key to uncover, when possible, hidden allergens and establish personalized avoidance strategies. Increased awareness and patient education are crucial in preventing future exposures and managing potential anaphylactic reactions effectively. Further research is required to better understand the mechanisms, prevalence, and clinical spectrum of allergic reactions to aromatic herbs in order to improve diagnostic strategies and optimize patient care.

Funding

No external funding.

Ethics approval

Not applicable. Patient’s informed consent for publication was obtained.

Conflict of interest

The authors declare no conflict of interest.

References