Most blisters develop where the outermost layer of skin is very thick, such as on the hands and feet.
As the feet are filled with many nerves and blood vessels and are under pressure most of the waking day, blisters on the feet can be especially painful. Depending on where a blister is on the foot, it can be disabling and hard to treat.
In this article, we look closely at the causes and treatment options for blisters on the feet.
Causes and symptoms
Blisters may appear as a response to injury or infection, and may be caused by friction against the skin.
Friction against the skin is what causes most blisters. However, anything that results in tissue or blood vessel damage to the outer skin can cause a blister.
Causes of blisters on the feet include:
Friction and pressure
A mixture of friction and pressure causes a majority of blisters on the feet.
When the skin of the feet is continually rubbed against a shoe, sock, or rough surface, irritation and inflammation often occur. The result is pain, swelling, and redness.
A red sore will usually develop on the foot before the blister itself. If the sore continues to be irritated or pressure is put on it, shearing of the skin occurs.
Shearing is where inflammation causes small tears in the skin. The body sends fluids to fill this opening and protect the more delicate, underlying tissue layers.
Friction blisters tend to be painful and tender to the touch and can be disabling.
When the skin is burned, the body may respond by creating a blister to protect underlying tissue layers from being damaged.
It may take a day or two for blisters to develop after first-degree burns, such as those resulting from sunburn. With more severe types of burns, blisters appear immediately.
As they are caused by a very painful condition, the symptoms of burn blisters are not noticed by most people, or they cannot be distinguished from those of the burn. Burn blisters tend to heal by the time the burn itself has healed.
Extreme cold can cause frostbite, freezing and killing cells in the skin. When this happens, a blister develops to keep heat in the body.
Frostbite burns tend to appear immediately. As with burn blisters, most people have a hard time separating the symptoms of frostbite blisters from the symptoms of frostbite itself.
Contact dermatitis or skin inflammation can occur whenever the skin is exposed to an irritant. If exposure continues, contact dermatitis can progress to form a blister.
Severe allergens and irritants can also result in enough inflammation and pressure to cause blisters.
Blisters either appear immediately or shortly after exposure to the irritant or over time with gradual, low-dose exposure. Chemical burns can also lead to blister formation.
Common causes of these types of blisters include:
- insect bites and stings
- skin allergens
- chemicals in washing detergents
- chemicals in shower or bath skin cleansers
- chemical solvents or cleaners
- toxic chemical agents or gases used in warfare
- chemicals used in laboratory or clinical settings
Any condition that weakens the outer layer of the skin can make it more vulnerable to blisters. Blisters can also be a symptom of certain infectious diseases and disorders.
Common medical conditions and treatments that may increase the risk of blisters on the feet include:
- chicken pox
- eczema, including dyshidrotic eczema, which causes small, very itchy blisters on the edges of the toes and soles of the feet
- autoimmune conditions, such as bullous pemphigoid and pemphigus
- diabetic neuropathy or nerve damage, causing a loss of sensation or pain in the feet
- being overweight, which puts increased pressure on the feet
- antibiotic treatment
- blood-thinning medications
Ruptured blood vessels
When very tiny blood vessels in the epidermis of the skin break, they sometimes leak blood into the tissue layers, causing a blood blister. Blood blisters tend to occur when the skin is crushed or pinched.
Using an over-the-counter blister bandage to cover a blister may be a recommended treatment.
In most cases, the best way to treat blisters on the feet is to leave them alone. Most blisters heal after a few days with basic care.
It is important always to leave both clear and bloody blisters intact. While they can be painful, blisters are a natural defensive mechanism. They help reduce pressure and protect underlying tissues.
Blisters also help seal off damaged tissues and prevent bacteria, viruses, and fungus from entering the wound.
Once a blister develops, a person should stop putting pressure on it immediately. Once it has broken and drained, the area around the blister can be very gently washed with soap and water. People should then cover the area with a sterile, dry, breathable dressing, such as gauze or a loose bandage.
For chemical or allergy blisters, it is vital to immediately stop exposure to the irritant and thoroughly wash the skin.
Additional treatments for clear and blood blisters on the feet include:
- applying an ice pack, wrapped in a thick towel or blanket, to the blister gently, without pressure
- using over-the-counter blister bandages to cover the affected area
- raising the foot with a chair or pillow to reduce blood flow to the area and limit inflammation
- keeping the area as dry as possible to aid healing
- removing the footwear or socks that caused the blister
- applying antibiotic ointments or creams gently to the blister and surrounding skin
- cleaning the area and reduce inflammation and pain with over-the-counter solutions, such as hydrogen peroxide or apple cider vinegar
A few days after the blister has opened, a person should use a small pair of sterilized scissors or tweezers to remove the remaining dead skin. They should be sure not to pull too hard and tear healthy skin.
When to see a doctor
Anytime a blister becomes discolored, extremely inflamed, worsens, or does not heal after a few days, someone should speak to a doctor.
Blisters that are yellow, green, or purple have often become infected and require medical attention. Abnormally colored blisters may also be a symptom of more serious, underlying health conditions, such as herpes.
A doctor may drain infected, persistent, or extremely disabling blisters in their office. They will use a sterilized scalpel or needle and usually take a small sample of the blister contents for testing.
Often, topical or oral antibiotics will be prescribed to treat an existing infection and prevent further infection from occurring.
Wet feet, socks, or footwear may be risk factors for blisters.
Most blisters that develop on the feet are caused by a combination of rubbing and pressure. Some further factors are known to increase the likelihood of friction blisters.
Moisture, heat, and pressure all weaken the skin and make it more vulnerable to tearing. Ill-fitting socks or footwear tend to rub the skin raw at points of contact.
Risk factors for blisters on the feet include:
- humid or damp environments
- wet feet, socks, or footwear
- warm environments
- excessive sweating
- poorly-fitting socks or footwear
- new footwear or footwear that has not been broken in
- long-distance walking or running
- repeating a motion for longer than usual, such as walking 5 miles instead of 1 or 2 miles
- activities, movements, or exercises that mean moving back and forth or side to side continuously, as in contact sports
- wearing footwear not designed for the activity being done
- wearing thin, non-absorbing socks
- wearing shoes without socks
- orthopedic or sole inserts that have moved out of place or are new
- carrying a heavy object or load
- foot abnormalities that impact the fit of shoes or socks
- having dry skin
- age, as older skin becomes more delicate and prone to damage
- wearing socks made out of synthetic material, including polyester and nylon, which can stop air flow
For areas prone to blistering, applying moleskin or foot tape and talcum powder before an activity may reduce the chances of new wounds.
Some bandages also have empty holes, that can help cushion delicate skin or freshly healed skin.
Sole inserts or socks that offer extra padding can also help absorb and reduce pressure on the feet.
Gluing or taping down shoe inserts or orthopedics can also help reduce friction.
Taking these steps and avoiding the risk factors listed above can help people to reduce their chances of developing blisters on their feet.
If a blister does develop, the best thing to do is to protect it and allow it to heal in its own time.
If the blister does not heal, gets worse, or changes color, then the advice of a doctor should be sought.