Why does the sole of the foot turn black after soaking feet in potassium permanganate, and what should be done?

Potassium permanganate foot soaks causing blackening of the soles may be due to factors such as staining, subcutaneous capillary rupture, burns, allergies, or athlete's foot. Medical attention should be sought promptly, and improvement can be achieved through general treatments, medications, or other methods as directed by a physician. Specific analyses are as follows:

1. Staining

Potassium permanganate contains pigments. If these pigments deposit on the skin surface of the feet, they may cause discoloration of the soles, leading to a dark appearance. This is generally a normal phenomenon and the skin color usually returns to normal after thorough washing.

2. Subcutaneous Capillary Rupture

Using hot water during foot soaks may cause dilation of capillaries under the skin, potentially leading to capillary rupture and resulting in blackened soles. In most cases, this condition resolves spontaneously without requiring specific treatment.

3. Burns

If the water temperature is too high during foot soaking, it may cause scalding of the skin on the feet, leading to blackened skin on the soles, often accompanied by symptoms such as swelling and pain. Under medical guidance, topical treatments such as burn ointments, erythromycin ointment, or mupirocin ointment may be used.

4. Allergic Reaction

Allergies to items such as foot soak basins or towels may trigger localized allergic skin reactions, manifesting as redness, swelling, itching, and darkened skin. Patients may take antiallergic medications such as loratadine tablets, cetirizine hydrochloride tablets, or ebastine tablets as directed by a doctor.

5. Athlete’s Foot (Tinea Pedis)

Athlete’s foot is typically caused by fungal infection and symptoms include itching, flaking, blisters on the feet, and sometimes discoloration of the sole skin. It is recommended to use antifungal medications such as miconazole nitrate cream, terbinafine spray, or bifonazole cream under medical supervision to alleviate symptoms.

In daily life, it is important to get adequate rest, ensure sufficient sleep, avoid staying up late, and engage in moderate outdoor activities such as walking or jogging, which may aid in recovery.