Cleaning PG wounds can cause more problems, especially if they do "wound debridement" (scraping the necrotic tissue clear of the wound). Any injury to the wound results in worsening of the PG.
For a summary of common PG therapy, here is an extract from a paper:
Topical treatment is generally insufficient as monotherapy and used as supportive treatment for systemic treatment. Topical treatment includes topical or intralesional corticosteroids, tacrolimus ointment, intralesional cyclosporine, topical 5 aminosalicylic acid, nitrogen mustard or 0,5% nicotine cream[2,13].
Systemic treatment is started in most of the cases with corticosteroids (e.g., methylprednisolone 0.5–1 mg/kg/d) or cyclosporine (e.g., 5 mg/kg/d) alone and considered as first-line therapy. Stabilization of the disease is usually achieved within 24 hours. For cases refractory to first line therapy with concomitant inflammatory bowel disease, second line treatment includes biological response modifiers and immunomodulatory therapy. Tacrolimus, thalidomide, azathioprine, dapsone, mycophenolate mofetil and infliximab are shown to be effective in case reports or small series. In cases without associated disease, intravenous immunoglobulins, granulocyte and monocyte adsorption apheresis plasmapheresis and cyclophosphamide treatment are also reported to be effective.