Blisters are generally small, fluid-filled bubbles that appear just underneath the skin. Blisters are a common cause of foot pain, particularly in runners and other athletes. According to Foot Pain Explained, blisters most often appear on the bottom of the foot, but they can also be found along the sides or on top. Either an injury to the skin or disease causes the top layer of skin, the epidermis, to separate from the middle layer, the dermis, and the space in between skin layers fills with fluid as a protective measure.
Friction and Burns
Usually, a blister forms as a result of friction and pressure, possibly from shoes that are too tight or repetitive rubbing. A blister contains a clear fluid, but if there is an injury, it may contain blood. A burn may also cause a blister to form. If the blister results from a burn and becomes infected, it may contain pus. Treatment includes keeping the blister clean and possibly releasing the fluid to alleviate pain.
Althlete's Foot Infection
An athlete's foot infection, also known as tinea pedis, can be the cause of small blisters on the bottom of the foot. According to MedlinePlus, an athlete's foot infection occurs when a particular type of fungus grows on the skin. These fungi thrive in warm and moist places like the feet. The skin may form tiny blisters that are itchy at first and then crack open, making a crusty rash. Athlete's foot can be treated with a number of over-the-counter antifungal medications.
Dyshidrotic eczema is a skin condition that causes small blisters to form on the bottom of the feet and palms of the hands. According to MedlinePlus, dyshidrotic eczema is more common in women than men. Blisters, which become intensely itchy, last for approximately 3 weeks and are more prevalent during certain times of the year, especially in those who suffer from seasonal allergies. These blisters crack open as they heal, leaving patches of dry, scaly skin. Treatment includes oral antihistamines and steroid creams.
Contact Dermatitis and Poison Ivy
Contact dermatitis can cause small blisters to form on the bottom of the feet in response to an allergic reaction. According to the Merck Manuals for Health Professionals, chemicals and dyes used in shoe and sock manufacturing, fragrances used in detergents and soaps, and some oral and topical medications can cause blisters. Blisters can also form in reaction to poison ivy if the bottom of the foot is exposed. Treatment for this includes calamine lotion and oral or topical antihistamines.
There are some other conditions that can cause blisters to form on the soles of the feet. Hand, foot and mouth disease is a viral disease seen in some children. Along with blisters on the soles of the feet, there can be blisters on the hands and sores in the mouth.
Epidermolysis bullosa is an inherited disorder that is hallmarked by blister formation that is caused by the slightest amount of friction, particularly on the soles of the feet. Some diabetics suffer from bullosis diabeticorum, which is a rare skin condition where blisters erupt on the bottom of the feet, hands and legs.