Epsom salts help with swim blatter infections and some gill infections...
Michael, Can you post a pic so I can see the infection? Best action IMHO for MOST skin infections is Meth Blue + Metrondazole (5-Nitroimidazole) feed twice daily + a dash of Seachem's Prime all in a hospital tank. **Warning Meth Blue will stain clear sealers in the tank blue (And anything else it touches)
If that does not work other treatments could work but are more harsh for the fish.