Inhibition of irritation and contact hypersensitivity by ethacrynic acid

The immunosuppressive effect of topical ethacrynic acid (ECA) was tested on both the induction and elicitation phases of contact sensitization in a mouse model. ECA (0.5% in vehicle) reduced the sensitization response by >50% when the sensitizer was either dinitrochlorobenzene (DNCB), oxazalone (OX) or para-phenylenediamine (PPD), and was applied 1 day later to the ECA-pretreated skin site. The immunosuppressive effect of combining ECA with either hydrocortisone or with cis-urocanic acid was also tested. An additive suppressive effect was observed with ECA in both combinations. The effect of ECA (1% in vehicle) on blocking the elicitation phase was also examined in a mouse ear edema assay. ECA was highly effective in preventing the challenge response in mice previously sensitized to either DNCB, OX or PPD. ECA (1% in vehicle) was also tested for its ability to inhibit contact irritation. ECA (1% in vehicle) was highly effective in preventing ear edema due to topically applied skin irritants including arachidonic acid, capsaicin, lactic acid, phorbol myristate acetate, trans-retinoic acid, and sodium lauryl sulfate. ECA may be useful for both prophylaxis and therapeutic treatment of diverse skin conditions including contact dermatitis, eczema, and other related allergic skin disorders.