Background

We report here a new unpublished treatment for dermatitis, due to contact with pine processionary caterpillar. This treatment, contrarily to those actually used, shows a prompt satisfactory response without secondary effects.

Case presentation

A 65-year-old man presented with complaints of pruritus in both forearms. He had come in contact with pine processionary caterpillars. A clinical diagnosis of contact dermatitis secondary to contact with pine processionary caterpillars was made. Cutaneous examination revealed erithematous plaques formed by the confluence of diffuse urticariform papules (figure 1A). Three h after exposure to caterpillars, a potassium dobesilate 5% cream prepared as previously reported1 at the pharmacy department of the Hospital Universitario Ramón y Cajal in Madrid, Spain, was self-applied by the patient twice a day for 2 days. After 1 day of treatment, skin lesions decreased and pruritus disappeared. A near complete disappearance of erithematous plaques was observed at 2 days of treatment (figure 1B). Three weeks later, the patient reported that complete resolution of skin lesions remained without further clinical manifestation or drug-related side effect.

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Figure 1

Improvement of contact dermatitis due to pine processionary caterpillars. An improvement of erithematous lesions was observed as early as 2 days after dobesilate topical application (B) compared to baseline conditions (A).

Treatment

This is the first case demonstrating the efficiency of using topical application of potassium dobesilate 5% cream, a specific inhibitor of fibroblast growth factor (FGF) in contact dermatitis.

Discussion

Skin contact with pine processionary carterpillars is a public health problem of increasing significance that causes dermatitis usually located in exposed areas. Recently the existence of an immediate hypersensitivity mechanism has been demonstrated, mainly in occupationally exposed people.2 Systemic symptoms, such as vomiting, abdominal pain, hypertension or anaphylaxis have only rarely been reported. The skin histology of caterpillar exposure typically shows epidermal oedema, superficial perivascular lymphocytic infiltrate and eosinophils.3 Eczematous reactions are typically treated with mild-to high topical steroids. However, response to topical steroids is often ineffective.4 Urticarial reactions may be treated with oral antihistaminics but a number of reports document the failure of antihistaminics to relieve itch.4 However, these standard treatments are maintained at least for 1 week.

Activated endothelial cells are critically involved in the pathogenesis of inflammation which is characterised by vasopermeability, plasma leakage and leucocyte recruitment. Therefore, inhibitors of activated vascular endothelium could reduce inflammation.5 Acute dermal plasma leakage after processionary contact contributes to oedema formation.6 Vascular endothelial growth factor (VEGF) is 10 000 times more potent than histamine for inducing skin plasma leakage. In dermatitis, production of VEGF is increased. VEGF acts as a proangiogenic factor and induces hyperpermeavility of blood vessels, and several reports have suggested that inhibition of its production or blockade of its activity may be an effective new therapeutic strategy for treating dermatitis.7 Recently, we have reported that dihydroxyphenylsulfonate (dobesilate; Doxium) inhibits acute VEGF-induced plasma leakage in rats8. Thus, the rapid effect of topical application of dobesilate against contact caterpillar dermatitis could be explained by its inhibitory effects on VEGF which is upregulated in dermatitis9,–,11. On the other hand, accumulating experimental evidence supports a role of FGF in inflammation12,–,15. In this case report we evaluated the effects of dobesilate, which is also a new well-characterised and efficient synthetic FGF inhibitor,16 on inflammation induced by contact hypersensitivity reactions to pine processionary caterpillars. The early application of the treatment could contribute to the rapid effects of dobesilate but it should be also considered that, as mentioned above, dobesilate has been shown to inhibit acute events in skin inflammation such as vascular permeability.8 As far as we know, there are no reports on caterpillar contact dermatitis treated with topical dobesilate. Our patient showed a good and prompt response to treatment suggesting that topically applied dobesilate is of help in contact dermatitis.