Skin moisture drops then recovers after allergen test in atopic dogs

Abstract

BACKGROUND: A defective skin barrier occurs in dogs with atopic dermatitis, and there is controversy over whether this defect pre-exists, or is secondary to allergic inflammation. OBJECTIVES: To study if an allergen challenge decreases the natural moisturising factor (NMF), which contains the main filaggrin degradation products. ANIMALS: Four house dust mite (HDM)-sensitised adult atopic dogs from a research colony. METHODS AND MATERIALS: Dogs were challenged epicutaneously with HDMs on the right lateral abdomen while the left thorax served as control. We swabbed the skin surface before, and at days (D)1, D2, D3, D7 and D28 after challenge, on both selected sites; swabs were soaked in detergent and frozen until assayed. The NMF components were measured by liquid chromatography-tandem mass spectrometry (LC/MS-MS). RESULTS: The allergen challenge induced moderate skin lesions at the application sites, and also mild erythema at the control areas. The allergen provocation led to significant decreases in the total NMF and its components trans-urocanic acid (t-UCA), pyrrolidone carboxylic acid (PCA) and serine on both sites. Lesion scores abated by D7 and the NMF concentrations had re-increased by D28. Skin lesion scores correlated negatively with the total NMF, t-UCA and PCA concentrations. CONCLUSIONS AND CLINICAL IMPORTANCE: In this experimental model, a single epicutaneous allergen challenge led to a transient and reversible decrease in skin surface NMF and its components, and concentrations were negatively correlated with skin lesion scores. These observations suggest that some of the skin barrier anomalies seen in atopic dogs likely develop secondarily to the underlying cutaneous allergic inflammation.