Environmental Dermatology

Botanical Briefs: Primula obconica Dermatitis

Author and Disclosure Information

Primula obconica, a household plant originally found in China that was introduced in Europe in the 1880s, has been reported to cause plant-induced contact dermatitis (CD). The condition more commonly is reported in Europe and less frequently in the United States, where the plant is not commonly included in patch testing protocols. Clinical features of P obconica CD can include facial and hand as well as fingertip dermatitis. The main allergens known to cause these findings are primin and miconidin. Treatment of P obconica CD mainly involves avoiding contact with the plant and applying a topical steroid.

Practice Points

  • Primula obconica is a household plant that can cause contact dermatitis (CD). Spent blossoms must be pinched off to keep the plant blooming, resulting in fingertip dermatitis.
  • In the United States, P obconica is not a component of routine patch testing; therefore, it might be missed as the cause of an allergic reaction.
  • Primin and miconidin are the principal allergens known to be responsible for causing P obconica dermatitis.
  • Treatment of this condition is similar to the usual treatment of plant-induced CD: avoiding exposure to the plant and applying a topical steroid.


 

References

Etiology

Calcareous soils of central and southwest China are home to Primula obconica1 (also known as German primrose and Libre Magenta).2 Primula obconica was introduced to Europe in the 1880s, where it became a popular ornamental and decorative household plant (Figure).3 It also is a frequent resident of greenhouses.

Primula obconica (also known as German primrose and Libre Magenta).

Primula obconica (also known as German primrose and Libre Magenta).

Primula obconica is a member of the family Primulaceae, which comprises semi-evergreen perennials. The genus name Primula is derived from Latin meaning “first”; obconica refers to the conelike shape of the plant’s vivid, cerise-red flowers.

Allergens From P obconica

The allergens primin (2-methoxy-6-pentyl-1,4-benzoquinone) and miconidin (2-methoxy-6-pentyl-1, 4-dihydroxybenzene) have been isolated from P obconica stems, leaves, and flowers. Allergies to P obconica are much more commonly detected in Europe than in the United States because the plant is part of standard allergen screening in dermatology clinics in Europe.4 In a British patch test study of 234 patients with hand dermatitis, 34 displayed immediate or delayed sensitization to P obconica allergens.5 However, in another study, researchers who surveyed the incidence of P obconica allergic contact dermatitis (CD) in the United Kingdom found a notable decline in the number of primin-positive patch tests from 1995 to 2000, which likely was attributable to a decrease in the number of plant retailers who stocked P obconica and the availability of primin-free varieties from 50% of suppliers.3 Furthermore, a study in the United States of 567 consecutive patch tests that included primin as part of standard screening found only 1 positive reaction, suggesting that routine patch testing for P obconica in the United States would have a low yield unless the patient has a relevant history.4

Cutaneous Presentation

Clinical features of P obconica–induced dermatitis include fingertip dermatitis, as well as facial, hand, and forearm dermatitis.6 Patients typically present with lichenification and fissuring of the fingertips; fingertip vesicular dermatitis; or linear erythematous streaks, vesicles, and bullae on the forearms, hands, and face. Vesicles and bullae can be hemorrhagic in patients with pompholyxlike lesions.7

Some patients have been reported to present with facial angioedema; the clinical diagnosis of CD can be challenging when facial edema is more prominent than eczema.6 Furthermore, in a reported case of P obconica CD, the patient’s vesicular hand dermatitis became pustular and spread to the face.8

Allergy Testing

Patch testing is performed with synthetic primin to detect allergens of P obconica in patients who are sensitive to them, which can be useful because Primula dermatitis can have variable presentations and cases can be missed if patch testing is not performed.9 Diagnostic mimics—herpes simplex, pompholyx, seborrheic dermatitis, and scabies—should be considered before patch testing.7

Prevention and Treatment

Preventive Measures—Ideally, once CD occurs in response to P obconica, handling of and other exposure to the plant should be halted; thus, prevention becomes the mainstay of treatment. Alternatively, when exposure is a necessary occupational hazard, nitrile gloves should be worn; allergenicity can be decreased by overwatering or introducing more primin-free varieties.3,10

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