Occupational asthma caused by carnation (Dianthus caryophyllus) with simultaneous IgE‐mediated sensitization to Tetranychus urticae

Tetranychus urticae (TU) is a known occupational allergen which frequently parasitizes carnations (Dianthus caryophyllus) (1). Therefore, the investigation of occupational allergy caused by carnation implies nonconsideration of TU as a causative agent. A case of occupational respiratory allergy to carnation, with simultaneous sensitization to TU in the same patient, is described. A 29-year-old woman, smoking 15 cigarettes per day, with neither personal history of atopia nor other antecedents of interest, having been employed at a flower supplier during the previous 2 years, was studied at our allergy unit. She had sneezing, rhinorrhea, coughing, wheezing and dyspnea while cleaning carnations at the flower shop. She also showed no respiratory symptoms in relation with other flowers. During holidays the patient was totally asymptomatic. Two carnation extracts, from petals and stems, were prepared (ALK-Abelló, Madrid, Spain). Only fresh flowers not infested by TU were used. Additionally, two TU extracts, from TU scratched from infested carnation leaves (TU-S) and from isolated bodies of TU (TU-B) were obtained (BIAL-ARISTEGUI, Bilbao, Spain) as previously described (1). Skin prick tests (SPT) with carnation stem (at 5% w/v), petal (at 2.5% w/v) and the two TU (at 1 mg/ml) extracts were positive. Simultaneously, negative response was obtained with a battery of frequent inhalants. SPT with carnation and TU extracts were negative in 10 atopic and 10 nonatopic patients who were used as control subjects. Total IgE was 203 kU/l. Serum-specific IgE [radioallergosorbent test (RAST)] to both petals and stem extracts was RAST class 3. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDSPAGE) immunoblotting showed two IgEbinding bands of 25 and 28 kDa present both in carnation petal and stem extract. In both TU extracts, four protein IgEbinding bands of 67.1, 48.8, 33.7, and 18.8 kDa were visible. Thirteen additional bands, ranging from 16.9 to 83.0 kDa, were detected in the TU-S extract which may be due to a contamination with carnation allergenic proteins. Metacholine challenge test showed bronchial hyperreactivity (5 mg/ml). Specific bronchial provocation test with a dilution of 1/64 of carnation stem extract (10% w/v) was positive, eliciting a dual response. Occupational asthma caused by carnation was diagnosed. As bronchial challenge test with TU-B extract was negative, being administered the maximum concentration of 1 mg/ml, asthma from TU could not be confirmed. In this case, a subclinical sensitization to TU or rhinitis caused by TU is possible. Additionally, it cannot be ruled out that administering higher TU doses during bronchial challenge test might have triggered an asthmatic reaction. Respiratory allergy to carnation has been described before (2–4) and, in this latest paper, a simultaneous sensitization to TU in the same patient is proved. Nevertheless, in the two latest articles there is no mention of the use of extracts from flowers in which parasitization by TU had been ruled out. However, it is important to keep this in mind in order to reach the right etiology, given that carnation industry workers may be doubly sensitized, as described above, or even to be sensitized to TU, but not to carnation proteins as proved by Delgado et al. in 16 workers who handled carnations at a greenhouse (1). Vidal et al. (2) proved type-I hypersensitivity to proteins from carnation and other flowers in a patient, without considering allergy to TU. However, bronchial provocation test was not performed because the patient showed rhinitis but not asthma. This case proves that in carnation workers showing respiratory symptoms, it is essential to investigate the flowers and their parasite TU separately, given that, either one of them, or both simultaneously, could act as an occupational allergen. We thank Margarita Encinas, Mercedes Lucı́a and Nuria González, nurses of Hospital of Segovia. The authors are indebted to Dr Julio Delgado (Hospital Univ. Virgen Macarena, Sevilla, Spain) for kindly providing TU samples for extract preparations and also to Alejandro Enrı́quez de Salamanca for the English correction of the manuscript.