Brown spots on bottom of feet can be something as simple as age spots or hyper-pigmentation or it can be a symptom of serious underlying diseases.

A few causes of brown spots on bottom of feet along with the associated signs and symptoms and treatment options are mentioned below:

1. Foot melanoma

Melanoma is an aggressive type of cancer that commence in skin cells responsible for skin color or pigmentation. It can affect individuals of all age groups. The cancer often goes undetected in the early stages, while treatment at later stages is very difficult. Hence it is vital to consult a doctor whenever dark spots appear on bottom of feet.

The signs and symptoms of foot melanoma are listed below:

• The spots may be asymmetrically shaped, i.e., one half of a brown spot on bottom of feet may be of different shape or size than the other half.
• It is not necessary for all the spots to be brown in color; they can be a mix of varied colors
• The borders are ragged, irregular, blurred, or notched
• The spots tend to grow in size. Hence, spots that are over 5 mm in size need to be immediately checked by doctor.

It is postulated that melanoma may develop due to increased exposure to sun. Other factors which may increase the risk to the cancer include:

• Formation of moles all over the body, especially if they occur at young age
• Red or blonde tresses
• Skin that easily develops freckles; very fair skin
• Any kind of sunburn that causes blistering and occurs before the person is 18 years old

Treatment of brown spots on bottom of feet caused by foot melanoma include

• Surgical removal of specific local lymph nodes and/or other surgeries
• Radiation therapy, chemotherapy, immunotherapy, and/or targeted therapy

2. Tinea Nigra

It is a fungal infection often caused by fungus called Phaeoannellomyces werneckii. The fungi destroy the melanin thereby causing pigmentation of skin and formation of brown spots on bottom of feet.

Signs and symptoms of tinea nigra include:

• In addition to brown spots on bottom of feet, patients may also experience such abnormal spots on the palms, neck, or chest.
• The spots (rash) are oval or slightly circular. It may be a lighter or darker shade of brown or even black
• The healthy skin is delineated from the dark spots by a distinct border

Landscape workers, gardeners, or others who work in the soil are at greater risk to developing this fungal infection. Hence, it is important for such people to wear thick gloves and shoes.

Brown spots on bottom of feet caused by tinea nigra are by use of topical antifungal creams with miconazole, ketoconazole, terbinafine, and clotrimazole as ingredients. Treatment usually finishes in 2 to 4 weeks but in severe cases the infection may clear up in about 8 weeks. In some cases doctors may use a scalpel to scrape the bottom of feet so as to facilitate easier penetration of skin by the cream and quicken the process of healing.

3. Plantar warts

Another cause of brown spots on bottom of feet is plantar warts. It is a disease caused by HPV or human papillomavirus infection. The virus can gain entry via tiny cuts in skin and hence can be contracted in swimming areas, public showers, locker rooms, or other moist and warm places. The virus can even transfer if you walk barefoot in contaminated areas in public, or by shaking hands with someone whose hands were soiled with the virus after he/she scratched the warts.

Signs and symptoms of plantar warts are:

• The brown spots on bottom of feet are tiny and appear like pin points
• Patients may experience pain and tender in feet when standing or walking
• The bottom of feet may develop a small, grainy, and ragged lesion
• Formation of a thickened solid skin callus over a clear area; it is an indication of an inward growing wart
• Distinctly visible lesion on feet

Untreated instances of warts may disappear only after many years. Patients may opt for OTC wart-removers, duct tape, salicylic acid or other kinds of home remedies to get rid of the warts. If issue persists, seek medical treatment which may involve the following:

• Topical acids
• Minor surgery to remove the warts
• Use of liquid nitrogen to freeze off the warts
• Bigger warts are removed via laser surgery

4. Hyper pigmentation

It is milder cause of brown spots on bottom of feet. It may be accompanied by rough, flaky, and dry skin. It can be treated by replenishing the foot skin’s moisture with home remedies like:

• Daily massaging of the feet with a foot scrub made from strawberries, chunky coarse sea salt, and comforting oils like jojoba oil, apricot oil, olive oil, or almond oil.
• Apply Vitamin E oil on feet and leave it overnight. Wash with lukewarm water in morning.
• Vitamin E liquid or Shea butter can lighten the brown spots. Use of pumice stone to scrub the feet is helpful.

5. Other causes

• Brown spots on bottom of feet may also be caused by diseases like purpura, diabetic dermopathy, arsenic poisoning, and athlete’s foot