Potassium permanganate is a highly caustic chemical, a strong oxidizer, and can be very harmful to tissues. It is also a poison. Its use for self medication is safe only in liquid form with solutions containing not to exceed 0.04 percent of potassium permanganate. Weak dilutions are safe for use in topical and external applications to the skin only.
It is commonly used as a disinfectant because of its excellent bactericidal and fungicide properties. It is also used as an algaecide and molluscicide. Its toxicity in its pure chemical form is rated as highly toxic by the acute rating from the US EPA product label. It is not listed as a carcinogen, as a human reproductive and developmental toxin, or as a chemical which can cause endocrine disorders in any watch list by a major health organization.
Potassium permanganate is commonly used as a treatment for skin conditions such as eczema, canker sores, dermatitis, acne, vaginal thrush, vulvovaginitis, and urine infections. Preparing a potassium permanganate bath is a popular remedy for dermatological conditions. It is also used as a wet soak for open sores and blistering wounds. For hair dye allergies, compresses of 1/5,000 potassium permanganate solution can be applied to the affected area.
Again, the need for accurate solution preparation is very important. Potassium permanganate baths must be around the 1/10,000 ratio which results to pleasant pink colored bath. For wet soaks, your solution must be 1/1,000. For severe cases of athlete's foot, prepare a 1% potassium permanganate hot foot soak solution since it is also an effective fungicide and may just be the treatment you are looking for!
On slightly different note, potassium permanganate is known to leave unsightly and annoying stains on your towels, flannels and even the bath tub not to mention your nails and skin. These can easily come off using an efficient household cleaner. As for the nails, just wash thoroughly with water and mild soap and you're good to go.