In Korea, lacquer, exudates obtained by cutting the bark of Rhus verniciflua Strokes, has a wide variety of traditional applications, including the decoration of ornaments, furniture or dishes. Urushiol is also a key ingredient of lacquer boiled chicken, a dish that is thought to improve health1. According to Korean traditional herbal medicine, the ingestion of lacquer is thought to be an effective treatment for gastrointestinal diseases and is thought benefit the general health2,3. But lacquer, due to the presence of urushiol, a compound prevalent in plants of the genus Rhus, can cause localized contact dermatitis as a result of direct contact with the skin, and the ingestion of lacquer may cause systemic contact dermatitis (SCD), as a result of the active compound reaching the skin via the circulatory system4. Although there have been many case reports of SCD due to the ingestion of lacquer, in light of the fact that lacquer tree is still widely eaten by the Korean people, there is a need for a systematic study of the clinical features and laboratory findings of SCD. Especially in Chungcheongnam-do, eating lacquer tree sprouts in spring is a regular custom, and the frequency of developing SCD, due to their ingestion, is similar to that of lacquer-boiled chicken. This study reviewed and analyzed the clinical features and laboratory findings of 33 patients, who had developed SCD, after ingesting lacquer in the province of Chungcheongnam-do.

Thirty-three patients, presenting with SCD in the Department of Dermatology at Soonchunhyang University Hospital, in Cheonan between Jan 2010 and June 2010, were enrolled in this study. All the patients involved were confidently considered to have developed SCD, due to ingestion of the lacquer as a result of their history and the time of onset. In this study, data were obtained from the retrospective study of patient's medical records. For general histories of the patients, we reviewed admission medical records for the admitted patients, and the outpatient clinic records for those patients treated in an out-patient clinic. General history included history of allergy to lacquer, the reason for and the way of ingestion, the type of skin lesion, and the general symptoms. Routine laboratory examinations, including a complete blood count, urinalysis, liver function tests, renal function tests and serum immunoglobulin E (IgE) level, were performed for some patients. We classified the skin manifestations into four groups: a localized or generalized erythematous maculopapular type, an erythema multiforme type, an erythroderma type and a separate group for other skin lesions (purpura and petechia, pustules, wheals or vesicles).

Allergic contact dermatitis (ACD) is ordinarily caused by an external exposure of the skin to an allergen5. In people who have been presensitized to an allergen by previous external exposure, the ingestion, injection or inhalation of the same allergen may result in SCD, which develops when the allergen reaches the skin via the circulatory system6. ACD has been well established as a type IV immune reaction, and SCD is known to be caused through an immune system, by a wide range of substances, such as plants, including Rhus spp., food additives, and antibiotics (eg. penicillin, neomycin, streptomycin and sulphonamades), as well as other drugs (eg. NSAIDs, acetyl salicylic acid, oral hypoglycemic agents, phenothiazines and benzodiazepines)7.

Most studies of ACD have considered poison ivy, which has urushiol produced by plants in the genus Rhus8. The genus Rhus contains over 150 species, with a global distribution covering most of the subtropical areas. Of which, about 30 species are thought to sensitize humans. In Korea, there are six Rhus species: R. javania Linne (var chinensis), R. ambigua Lavalle (T. radicans), R. succedanea Linne (T. succedaneum), R. trichocarpa Miquel (Japanese sumac), R. sylvetrius Sieb. Et Zucc. (woodland sumac) and R. verniciflua Stokes (T. vernicifluum). Among these species, R. verniciflua is the most common cause of 'Rhus dermatitis' in Korea9,10. Lacquer is obtained by tapping the tree sap through incisions in the bark. The raw sap (oleoresin) from the incised trees contains urushiol, the active antigenic component of genus Rhus. Urushiol acts as hapten and exhibits antigenicity, which binds with a self-protein. Urushiol contains a mixture of pentadecylcatechol (PDCs), and is comprised of either a C15 or C17 alkyl or alkenyl group on the side chain11,12. Both, the saturated and unsaturated, side chains were identified and the basic molecule of PDC has a completely saturated side-chain at position 3. Desaturation of the side-chain leads to a greater antigenicity. Urushiol reacts with self-protein at the catechol phenol ring and with unsaturated side chain sites10,11,13.

In East Asia, the use of lacquer for the decoration or protection of furniture, floors, tea-pots and ornaments is a widespread, and traditional, practice2. Many Koreans ingest lacquer in various forms, such as lacquer-boiled chicken, a sap drink, and lacquer tree sprouts, because they are thought of as an effective treatment for gastrointestinal diseases, and generally, benefit the health. For these reason, in contrast to other countries, lacquer-related illnesses in Korea are mostly caused by the ingestion of lacquer, which results in SCD, rather than ACD1-3. Lacquer-boiled chicken, a traditional dish that consists of chicken boiled with the bark, branches and stem, is the commonest manner of lacquer ingestion in Korea. Although our study also showed that lacquer-boiled chicken was the most common way of lacquer ingestion, there were also many people who ate lacquer tree sprouts (14/33: 42.4%), due to seasonal and local factors. The data of this study were collected during the spring, and many Koreans in Chungchoengnam-do, more than in other areas, conventionally eat lacquer tree sprouts during this time in the belief that it can help overcoming spring fever.

In our study, SCD resulting from the ingestion of lacquer was slightly more common among women, which has been corroborated by another study that had a similar sex ratio3. However, in another study, male patients outnumbered the female patients14. Our patients were aged between 27 and 74 years old, suggesting that traditional folk food is not consumed solely by older Koreans. The patients also had a wide range of occupations. The most commonly affected group was the housewives, but some patients were highly educated professionals. One third (11/33) of the study population ingested lacquer as a health food, and 15.2% were persuaded by their friends or spouse. These findings suggest that Koreans, regardless of their age, sex and occupation, still consider traditional herbal food, including lacquer, to be an effective means of some disease and health.

The generally reported cutaneous manifestations of SCD are eczema, pompholyx and/or a symmetrical maculopapular rash, but rarely reported cases have presented with vasculitis or fixed drug eruption, erythema multiforme15. Systemic manifestations, such as headache, fever, nausea, vomiting, diarrhea have also been reported3,6. Park et al.3 classified the skin eruptions associated with SCD into three types: a localized or generalized erythematous maculopapular rash type, which was most common, an erythema multiforme (EM) type and a generalized erythroderma type. Although EM is a rare symptom of SCD in general, it has frequently presented in patients with SCD, resulting from the ingestion of lacquer. Similarly, Kim et al.4 reported that erythroderma was more frequently observed in patients with a known history of allergy to lacquer (4 of 10 patients) than in those without such history (2 of 21 patients).

In our study, out of the nine patients with a history of ACD from contact with lacquer, six (66.7%) developed systemic symptoms, and out of the 24 patients without such history, 13 (54.2%) exhibited systemic symptoms. These results suggest that, if ingested, lacquer can cause SCD even in patients without a known history of allergic reaction. This is strongly supported by a study by Park et al.16, in which 12% of the patients who had no previous history of lacquer allergy exhibited positive patch-test results. There can be possibilities of patient's ignorance of their previous exposure to lacquer or cross-reaction by pre-sensitization of other materials like ginkgo.

Urushiol is a very potent allergen and it commonly causes contact dermatitis, after exposure17, and it has caused great economic loss due to debilitation of the work force14. In Korea, contact dermatitis cases comprise 5~13% of dermatological outpatients, of these cases 18% are due to plants, with lacquer tree being the most common cause1,14,18. Generalized misconceptions and ignorance of the toxic nature of lacquer, combined with health official's indifference, regarding the public knowledge of these issues, is resulting in the continued ingestion of foodstuffs made from lacquer tree and developing SCD cases. SCD causes much more severe itching and debilitation than contact dermatitis resulting from direct exposure18.

Treatment of SCD is similar as the management of ACD, which is dependent on the severity of the symptoms, and consists of systemic antihistamines and corticosteroids. But prevention, which depends upon the avoidance of allergens, is the fundamental treatment6. To this end, there has been a recent attempt to produce urushiol removed foodstuff and drug by using a biological detoxification and heating, respectively19,20. However, this new product may still cause allergic reactions, although to a diminished degree12.

In conclusion, we found that SCD commonly occurs in Koreans after the ingestion of lacquer until now. In this study, the ingestion of lacquer-boiled chicken and the ingestion of lacquer tree sprouts were equally the most common way of lacquer ingestion in the province of Chungcheongnam-do. Although the Korean people are becoming more aware of the dangerous effects of lacquer-boiled chicken, which has been thought to be the most common way of lacquer ingestion in Korea, there is still little awareness of the dangers of other food stuffs, containing lacquer, such as sprouts. Our study highlights the importance of educating the people concerning the dangers of lacquer ingestion, considering regional factors. Furthermore, we would suggest that unsafe food, containing lacquer, should be banned.