Anti-inflammatory effects of aroma oil complex on DNCB-induced allergic contact dermatitis in dogs

Allergic contact dermatitis (ACD) is an inflammatory skin disease and regarded as a prototype of T-cell mediated delayed-type hypersensitivity reactions. Aroma Oil Complex (AOC) is composed of lavender true oil, chamomile roman oil and tea tree oil. This study was performed to assess the effects of AOC in a canine model of ACD. ACD was induced on the back of dogs induced by sensitization and repeated application by 2,4-dinitro-1-chlorobenzene (DNCB). Topical treatment of AOC was applied once a day for 8 days and skin biophysical parameters including transepidermal water loss (TEWL), skin hydration, skin thickness and erythema index, were measured every two days during experimental periods. Histopathology and immunohistochemistry were performed to evaluate the antiinflammatory effect. In skin biophysical parameters, TEWL, skin hydration, skin thickness and erythema index were significantly increased, with a maximum increase appeared on day 2 (p < 0.05). After the completion of AOC treatment, skin biophysical parameters were significantly reached those of baseline in a time-dependent manner (p < 0.05). In histopathology, marked increases of epidermal thicknesses were induced after DNCB challenge with numerous inflammatory cell infiltrations and edematous changes, decreases of connective tissue occupied regions in dermis. In addition, marked increases of cytokine - tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ)-immunoreactivities in the dermis and of apoptotic markers - caspase-3 and PARP-immunoreactivities in the epidermis were observed in DNCB control as compared with intact control, respectively (p < 0.01). The decrease of infiltrated inflammatory cells and related decreases of pro-inflammatory cytokine immunoreactivities were observed in AOC treated skin (p < 0.01). Based on these findings, AOC may have anti-inflammatory and alleviatory effects in the allergic contact dermatitis.