Abstract
Objective
To elucidate the actual circumstances of damage caused by Japanese Alocasia (A) odora.
Materials and Methods
We investigated cases in Japan from our own hospital in the eastern part of Shizuoka Prefecture as well as published reports.
Results
A. dorais found in western Japan, and plants of the Alocasia genus are cultivated often. A. odora is frequently associated with food poisoning because its aboveground parts resemble those of Satoimo (Colocasia esculenta). Moreover, A. odora contains insoluble calcium oxalate crystals, which cause poisoning symptoms, such as oral pain, nausea, vomiting, and laryngeal edema, resulting in near asphyxia, diarrhea following shock, and skin dermatitis. Calcium oxalate crystals are abundant in Araceae family plants, and cases of health damage owing to the accidental ingestion of Araceae plants have been reported worldwide.
Conclusion
Due to the strong irritation felt in the mouth upon contact with the plant, it is advisable to immediately spit out the plant and rinse the mouth. In addition to drug administration, ensuring a secure airway may be necessary if there is a risk of asphyxiation.
Keywords: Alocasia odora, poisoning, clinical course
Introduction
Alocasia (A) odora, (Japanese name: Kuwazuimo), is commonly known as Chinese Taro in English. This plant belongs to the order Alismatales, family Araceae, and genus Alocasia according to the Angiosperm Phylogeny Group classification system. The native habitats of this plant include the southern regions of Shikoku and Kyushu in Japan, the Ryukyu Islands, southern parts of China, Taiwan, the Indo Chinese Peninsula, and tropical to subtropical regions of India1). The plant typically grows in lowland evergreen forests, and plants of the Alocasia genus are often cultivated as ornamental plants. A. odora is frequently associated with food poisoning because its aboveground parts (leaves and petioles) resemble those of Colocasia esculenta1). There has only been one clinical case report of A. odora poisoning in South Korea2). To elucidate the actual circumstances of damage caused by Japanese A. odora, we investigated cases in Japan from our own hospital in the eastern part of Shizuoka Prefecture as well as published reports. Moreover, we documented the results for future studies.
Summary of Previous Literature and Our Cases
To identify reports of A. odora-related human poisoning, we initially conducted a search of the Ichushi database (Japana Centra Revuo Medicine), which is a collection of Japanese medical articles, using the keyword “A. odora” on October 20, 2023. We also searched the PubMed database using the same keywords to identify related articles. The study included the following parameters that were investigated using medical records or registration data: sex, age, month of presentation, symptoms of poisoning, cause of poisoning, and clinical course.
Subsequently, we conducted a retrospective study using registered data from our department to extract and analyze cases of suspected A. odora poisoning among all poisoning cases treated in our emergency department between October 2012 and September 2023. We used the keyword “A. odora” to select patients from the registered data.
A search in the Ichushi database revealed 13 relevant reports3,4,5,6,7,8,9,10,11,12,13,14,15). Our search of the PubMed database yielded six articles. Of these, only two described intoxication induced by A. odora. The first was a report written in Japanese that had already been found in a previous search (only the abstract was in English)10). In addition, there were five cases suspected of A. odora poisoning, including one patient’s spouse who completed a questionnaire and did not seek medical treatment in our department. We summarized the Japanese and English reports, along with our cases, in Table 1. Toda’s report compiled cases from 1961 to 201010), and Yanagawa’s report compiled cases from 2015 to 2023. Yanagawa’s report indicates the occurrence of the year in parentheses in Table 2.
Table 1. Cases in our hospital.
| Year of visit | Age (years) | Sex | Symptoms | Cause of misrecognition | Treatment | Outcome |
|---|---|---|---|---|---|---|
| 2023 | 87 | Male | Burning sensation in the oral cavity | Tried eating Kyoto-imo | Oral mouthwash | Admission for 2 days |
| 2019 | 34 | Female | Numbness in the oral cavity, difficulty breathing, and excessive salivation | Ate a simmered dish of taro harvested from the garden | Oral mouthwash | Admission for 4 days |
| 2017 | 43 | Female | Numbness in the oral cavity, shortness of breath | Ate the Zuiqui received from an acquaintance | Oral mouthwash | Return home |
| 2017 | NR | Male | Numbness in the oral cavity | Same as above | Oral mouthwash | Without seeking medical attention, untreated |
| 2015 | 67 | Female | Numbness in the oral cavity, shortness of breath | Ate decorative taro | Oral mouthwash, adrenaline, hydroxyzine | Return home |
NR: data not reported.
Table 2. Previous reported cases.
| Author | Year | Place | Number | Age (years) | Sex | Symptoms | Cause of misrecognition | Treatment | Duration of treatment |
|---|---|---|---|---|---|---|---|---|---|
| Ikeda3) | 2022 | Oita | 1 | NR | NR | Severe pain in the oral cavity | Hasuimo | Oral mouthwash | Over 2 days |
| Miyazaki4) | 2020 | Fukuoka | 1 | NR | NR | Pain in the oral cavity | Hasuimo | NR | NR |
| Takayama5) | 2020 | Miyazaki | 1 | NR | NR | NR | NR | NR | NR |
| Murakami6) | 2018 | Osaka | 2 | NR | 1 male, 1 female | Pain and numbness in the oral cavity, short of breath | Roots of homegrown plants | NR | NR |
| Kimura7) | 2016 | Tokyo | 1 | NR | NR | Sharp pain and numbness in the oral cavity | Satoimo | NR | NR |
| Shimoi8) | 2015 | Tokyo | 1 | NR | NR | Burning pain and numbness in the oral cavity | Rhizomes of houseplants | NR | NR |
| Sakamoto9) | 2015 | Saga | 1 | NR | NR | Severe pain in the oral cavity | Mizuimo | NR | NR |
| Toda10) | 2014 | All Japan | 64 (14 accidents) | NR | NR | NR | NR | NR | NR |
| Ikeno11) | 2012 | Kanagawa | 1 | NR | NR | Pain and numbness in the oral cavity, tongue swelling | Satoimo | NR | NR |
| Morioka12) | 2009 | Miyazaki | 1 | NR | NR | Numbness in the oral cavity | Hasugara | NR | NR |
| Ushiyama13) | 2004 | Tokyo | 2 | NR | 1 male, 1 female | Pain and numbness in the oral cavity | Wild yam | NR | NR |
| Kumano14) | 2001 | Nagasaki | 4 | NR | NR | Pain in the oral cavity | Hasuimo | NR | over 2 days |
| Kosaka1) | 2000 | Miyazaki | 1 | NR | NR | Swelling in the oral cavity | Satoimo | NR | NR |
NR: data not reported.
Epidemiology
Based on Table 1, the age distribution ranges from middle-aged to senior, and there appears to be no significant difference between the sexes.
A. odora poisoning in Japan has mainly been reported in its place of origin Kyushu1); however, cases have also occurred in major metropolitan areas, such as Tokyo, Kanagawa, and Osaka. Given that there were no previous reports of A. odora poisoning cases in Shizuoka Prefecture in our available data, this is the first report of its kind in this region.
Excluding A. odora, needle-like calcium oxalate crystals are abundant in plants of the Araceae family, and cases of health damage due to accidental ingestion of Araceae plants have been reported not only in Japan but also other countries16,17,18,19,20).
Mechanism of Action
A. odora contains insoluble calcium oxalate crystals, which affect poisoning symptoms when the needle-shaped crystals cause irritation (Figure 1). Recently, toxicity in the Araceae family has been attributed to several proteolytic enzymes that trigger the release of potent kinins and histamines by the body21). These kinins, subsequently cause several local reactions that may be aggravated by the sharp calcium oxalate crystals contained in plant tissues21).
Figure 1.
Calcium oxalate crystals.
Toxin Biosynthesis
Several pathways for oxalate production in plants have been hypothesized, including cleavage of isocitrate, hydrolysis of oxaloacetate, glycolate/glyoxylate oxidation, and oxidative cleavage of l-ascorbic acid22, 23). Plants absorb calcium ions and water from the soil through their roots. These ions then move within the plant body, where calcium ions combine with oxalate ions within the plant cells, leading to crystallization. Identification of the structural characteristics of calcium oxalate crystals contributes to understanding their protective and/or defensive functions against abiotic stress factors23).
Calcium oxalate crystals are present in various forms in plants, including needle-shaped raphides, pencil-shaped styloids, block-shaped crystal sand, rosette-shaped druses, and prism24, 25). Among them, needle-shaped raphide shave garnered the most attention. Calcium oxalate crystals in wild taro were needle-shaped, in contrast to the block-shaped crystals found in spinach24).
Clinical Manifestations
Calcium oxalate causes immediate symptoms, such as oral pain, nausea, vomiting, diarrhea, and skin dermatitis upon contact26, 27). Secondary dehydration, electrolyte imbalance, and shock are also possible21). Oral manifestations may resemble angioedema or anaphylaxis19). All patients in Table 1 complained of oral numbness and pain immediately after ingesting the suspected food. Moon et al. reported that two patients experienced oral numbness and intractable tongue pain, and one patient required endotracheal intubation because of upper respiratory tract obstruction2). Moreover, a dog died from asphyxia due to laryngeal edema after ingesting Dieffenbachia picta, which contains calcium oxalate, but not A. odora17). In addition, two patients in Table 1 required hospitalization, and one was discharged the following day. The remaining patient (a 37-year-old female) had the longest hospitalization period (four days); she had consumed a stew containing taro collected from her mother’s garden. After taking a bite of taro, the patient experienced discomfort in her mouth and developed the aforementioned symptoms. Upon arrival, she was in a semi-sitting position and unable to swallow saliva, resulting in drooling. Throat and laryngoscopies revealed pharyngeal ulcerations (Figure 2). Supportive treatment was administered, and the patient was admitted for observation. The patient’s condition improved, and she was able to resume eating on the third day of hospitalization, after which she was discharged.
Figure 2.
Oral cavity in Yanagawa’s first case (37-year-old female) in Table 1.
Diagnosis
Diagnosis involves the observation of insoluble calcium oxalate using an optical microscope and/or analysis of oxalate using high-performance liquid chromatography1). Previous Japanese reports have mainly focused on the identification of calcium oxalate (a toxic component of A. odora) through analysis of reports from health authorities. However, our cases primarily emphasized the clinical course, and we did not specifically detect calcium oxalate. In one case, the local health department was requested to analyze the remaining food, but this was deemed impossible. Therefore, the diagnosis is purely clinical.
Symptoms of A. odora Poisoning
Consider the possibility of A. odora poisoning when individuals display symptoms such as oral and upper airway irritation, instantaneous pain, swelling of the mouth, nausea, vomiting, abdominal pain, or skin irritation after exposure to the plant18).
Treatment
Due to the strong irritation felt upon contact with the mouth, it is advisable to immediately spit out the plant and rinse the mouth. The oral administration of activated charcoal may prevent the absorption of calcium oxalate21). Calcium from sources, such as milk, may also help precipitate soluble calcium oxalate21). Administering antihistamines may help alleviate symptoms21). If vomiting and diarrhea persist, leading to dehydration and shock, intravenous fluid therapy may be necessary. When there is a risk of asphyxiation due to laryngeal edema, intravenous administration of steroids, inhalation of drugs containing catecholamines or steroids, or oxygen therapy may be performed28). If there is no improvement, or if there is a high likelihood of progression to asphyxiation, immediate airway management with endotracheal intubation, cricothyroidotomy, or tracheostomy may be necessary to secure the airways. Additionally, because contact with plant sap can lead to dermatitis, the use of rubber gloves or similar protective measures is recommended when handling it to prevent direct skin contact.
Outcome
A. odora may cause poisoning symptoms, such as oral pain, nausea, vomiting, laryngeal edema resulting in near asphyxia, diarrhea following shock, and skin dermatitis, when the needle-shaped crystals cause irritation. To the best of our knowledge, there have been no reports of fatal cases of A. odora poisoning in humans.
Prevention
Considering that A. odora can be purchased nationwide as an ornamental plant through online shopping, it is expected that cases of A. odora poisoning may occur in areas outside its place of origin10). Therefore, preventing A. odora poisoning requires raising awareness among the general public about its dangers and educating them about proper handling and cooking methods. Providing information and raising awareness among healthcare professionals regarding the symptoms and diagnoses of A. odora poisoning is essential. These efforts could reduce the incidence of A. odora poisoning and enable prompt intervention if cases arise.
Conclusion
A. odora contains insoluble calcium oxalate crystals, which affect poisoning symptoms, such as oral pain, nausea, vomiting, and laryngeal edema, resulting in near asphyxia, diarrhea following shock, and skin dermatitis when needle-shaped crystals cause irritation. Calcium oxalate crystals are abundant in plants of the Araceae family, and cases of health damage owing to the accidental ingestion of Araceae plants have been reported worldwide. Due to the strong irritation felt upon contact with the mouth, it is advisable to immediately spit out the plant and rinse the mouth. In addition to drug administration, ensuring a secure airway may be necessary if there is a risk of asphyxiation.
Conflict of interest
We do not have conflict of interest to declare.
Funding information
This study was supported in part by a Grant-in-Aid for Special Research from Subsidies for ordinary expenses of private schools from The Promotion and Mutual Aid Corporation for Private Schools of Japan.
Ethics approval
The research protocol was approved by the Juntendo University Review Board (298).
Consent for publication
Not applicable.
Data availability statement
None.
Author contributions
All authors have made substantive contributions to the study.
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Associated Data
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Data Availability Statement
None.