Occupational allergic contact dermatitis due to Eucalyptus cinerea

Eucalyptus is commonly used in flower arrangements as greenery. Oil derived from the plant is frequently used in aromatherapy, pharmaceuticals due to its anti-bacterial and immunomodulatory properties.1, 2 Allergic contact dermatitis (ACD) due to eucalyptus is uncommon but may present as severe cutaneous reactions. We present two rare cases of female florists with ACD to eucalyptus plants. A 27-year-old female florist was referred due to a suspected severe flare up of atopic dermatitis (AD). Her history included AD and recurrent hand eczema. During the last 2–3 months, she had suffered from severe facial dermatitis, itchy eyes and exacerbation of her hand eczema, while handling flowers and plants. She presented with a moderate face, eyelid and hand eczema affecting the dorsal hands and interdigital areas. She had positive patch test reactions to eucalyptus leaf (1+ on D2 and 3+ on D3) and doubtful to the stem (+? on D3). A 40-year-old female florist was referred due to suspected occupational ACD. Her history included AD, allergic asthma, rhino-conjunctivitis and chronic hand eczema. During her 20-year career as a florist, her hand eczema gradually worsened with a severe exacerbation within the last 5 years, and a sensation of ‘stinging itch of the skin’ when near eucalyptus plants. Examination showed severe facial eczema with fissures (Figure 1), bilateral preauricular eczema and bilateral moderate interdigital hand eczema. She had strong positive reactions to eucalyptus leaf (3+ on D2) and stem (2+ on D2), Chrysanthemum (2+ on D5) and Fragrance Mix I (FMI) (2+ on D2), and doubtful reactions to Oak moss and Hydroxycitronellal (+? on D5). The patients were patch tested with the European Baseline Series, several extended patch test series, including eucalyptus oil 2% in pet (INCI-name: ‘Eucalyptus globulus leaf/twig oil’ and CAS no. 84625-32-1), the patients' cosmetic products and working gloves, Eucalyptus cinerea leaf and stem ‘as is’. We used Finn Chambers® (8 mm; SmartPractice®, Phoenix, AZ, USA) loaded with allergens from Chemotechnique MB Diagnostics AB (Vellinge, Sweden) and SmartPractice allergEAZE® (Hillerød, Denmark). The allergens were applied on the upper back and occluded with Norgesplaster® AS Scanpor tape (Vennesla, Norway) for 2 days. Readings were performed on Day 2 (D2), D3 and D7, according to ESCD-guidelines.3 Prick testing with Eucalyptus cinerea leaf and stem was negative. The positive patch test reactions to Eucalyptus cinerea ‘as is’ were evaluated as clinically relevant, and the patients were diagnosed with occupational ACD. The patients were instructed to avoid direct skin contact to eucalyptus plants by use of protective accelerator-free gloves. Both patients were treated with topical corticosteroids and tacrolimus ointment. Patient case 2 was also treated with oral methotrexate and folic acid, with good results. The eucalyptus plant originates from Australia and belongs to the flowering myrtle tree family, Myrtaceae. Eucalyptus oil is extracted from the leaves or twigs of the plant.4 Since 2011, eucalyptus oil is known as an ‘established contact allergen in humans’.5 None of our patients reacted to eucalyptus oil 2% in pet. According to De Groot and Schmidt, commercially available eucalyptus oils in Europe are made in China and derived from various eucalyptus-species, most commonly from the Eucalyptus globulus Labii.4 Furthermore, they state that the most prevalent ingredients in these oils are 1.8-Cineole (60.0%–80.0%), α-Pinene (1.0%–22.0%) and Limonene (1.0%–15.0%), but more than 250 different eucalyptus ingredients have been identified.4 The great diversity of species and ingredients might explain why the patients did not react to it. In addition, recent patch test results of essential oils by the IVDK-working group found that eucalyptus oil was among the essential oils with the lowest positivity rates.6 Only five cases of ACD caused by eucalyptus plants have previously been described (Table 1).7-10 Two of these patients were tested with eucalyptus oil8, 9 and one with eucalyptus oil ingredients7: all with negative results. Positive: Negative:b Positive: Negative: Positive: Positive: Positive: The presented cases highlight the importance of patch testing with the suspected plant allergen ‘as is’, given that its botanical properties are known. We speculate that the commercially available essential oils for patch testing might not sufficiently screen for the most common and clinically relevant culprit plant allergens, and that ACD due to eucalyptus might be underestimated. Sofia Botvid: Conceptualization; investigation; methodology; writing – original draft; writing – review and editing. Jakob Ferløv Schwensen: Investigation; methodology; writing – review and editing; supervision. Anne Birgitte Simonsen: Investigation; methodology; writing – review and editing; supervision. We would like to thank the two patients for letting us share their story, patch test results and clinical picture. The authors have no conflict of interest to declare.