What Causes Unexplained Blisters on Your Feet? (2024)

Blisters on feet are typically caused by friction. A blister (vesicle) is a small pocket of fluid that forms beneath the skin as a result of an injury, allergic reaction, or infection.

A common but usually mild ailment, foot blisters are uncomfortable and sometimes painful. Blisters can be round or oval and filled with clear or bloody liquid. The skin around the blister is usually red, warm, and tender to the touch.

Fortunately, most blisters heal on their own in a few days to a week. Blisters on the feet, however, have a high chance of breaking open, which can lead to an infection.

This article discusses blisters on the feet. It explains how blisters form and the different causes of foot blisters. It also provides details on how to prevent and help heal foot blisters and when to see a healthcare provider.

What Causes Blisters on the Feet?

Footwear is the most common cause of blisters on the feet. When your shoes repeatedly rub against your skin, it can cause a friction blister.

Friction

Wearing new, poorly-fitting, or loosely tied shoes or shoes without socks can cause them to rub against the skin. Spending several hours a day on your feet or walking or running long distances can also contribute to friction blisters.

Bunions, bone spurs, hammertoes, ganglion cysts, or other abnormal lumps on your feet can also lead to friction blisters. You can typically feel a friction blister forming.

Friction blisters occur from repeated rubbing against the skin. This causes the upper layer of skin to separate from the layers underneath. Fluid collects under the damaged skin and provides a cushion to protect the skin from further damage and allow it to heal.

How to Help Friction Blisters Heal

Most friction blisters heal on their own in about a week, provided you don’t re-injure them. These tips can help ensure it heals:

• Avoid wearing the same shoes that caused the blister again until the blister heals.
• Cover the blister with a loose bandage, moleskin, or foot pad. Don't put adhesive directly on the blister, which could tear the delicate skin. Instead, cut a hole that is slightly larger than the blister in the center of the moleskin or pad to protect it.
• Keep the area clean, dry, and covered. If the blister pops, do not remove the roof of the blister, which is protecting the skin underneath it.
  

Excessive Foot Moisture

Excessive moisture can clog the pores on your feet, which, in turn, can lead to the formation of blisters between the toes and anywhere moisture builds up. Blisters of these sorts are common in runners due to the accumulation of sweat in their shoes and socks.

How to Prevent Excess Foot Moisture

There are several things you can do to prevent the build-up of foot moisture:

• Wear moisture-wicking socks.
• Wear breathable shoes like sandals.
• Change your socks or shoes when your feet become moist or sweaty.
• Avoid shoes that trap moisture, such as leather boots, if you intend to wear them for a long time.
• Use foot antiperspirant to reduce sweating.

When blisters form due to excess moisture, they can become more susceptible to infection. Keeping your feet dry can help prevent this.

Sunburn

A sunburn is caused by overexposure to the sun’s ultraviolet (UV) rays. It can occur on almost any part of the body, including the tops of your feet.

Sunburn blisters can be extremely painful and may develop quickly based on your skin type, season, geographic location, and time of day you are in the sun. People often get these blisters when they fall asleep in the sun.

How to Help Sun Blisters Heal

Sunburn blisters usually heal on their own, but you can help speed your recovery in several ways:

• Do not pop blisters as this can lead to infection.
• Use a cold compress or take a cool shower to ease the pain.
• Take an over-the-counter pain reliever like Tylenol (acetaminophen).
• Apply aloe gel to cool the feet and relieve pain.
• Avoid further sun exposure by wearing socks when outdoors.
• Drink plenty of water since blisters can cause your body to lose moisture and lead to dehydration.

Allergic Contact Dermatitis

Allergic contact dermatitis is a type of rash that occurs when you come into contact with an allergy-causing substance, known as an allergen. The rash can develop within minutes to hours of exposure and last up to four weeks in some cases. Tiny blisters are common.

You can get allergic contact dermatitis by walking barefoot through poison ivy. If you have a latex allergy, shoes made with latex rubber can trigger a reaction. Similarly, socks made with copper-infused fibers can also cause a rash with blisters if you have a metal allergy.

How to Prevent Allergic Contact Dermatitis

The best way to prevent allergic contact dermatitis is to avoid known allergens. If contact does occur, you can use topical corticosteroids (steroids) to reduce inflammation and itching. Severe cases may need oral steroids like prednisone.

Psoriasis

Psoriasis is an autoimmune disease that causes itchy and scaly red patches on the skin. Although the patches are most common on the knees, elbows, torso, and scalp, they can also develop on the hands and feet.

Psoriasis occurs because the immune system is overactive and speeds up skin cell growth. This causes cells to accumulate faster than they can be shed, causing thick, flaky areas of skin called plaques. Tiny blisters can form as fluids beneath the skin start to pool.

A rare form of psoriasis, known as pustular psoriasis, can cause white or yellow blisters filled with pus. When it affects the feet, it is called palmoplantar pustular psoriasis.

How to Manage Foot Psoriasis

The following medications and therapies can help reduce the symptoms and discomfort of foot psoriasis:

• Occlusive steroid therapy involves covering the foot with plastic after applying steroid cream.
  
• Oral retinoids are drugs taken by mouth that slow skin cell growth
  
• Topical calcineurin inhibitors are drugs that suppress the immune response.
• Phototherapy uses a special band of UV light to slow skin cell growth.

Dyshidrotic Eczema

Although dyshidrotic eczema typically affects the hands, it can also cause blisters on the soles of the feet. The outbreak of blisters, which resembles tapioca pudding, can flare up suddenly and resolve just as quickly. Young adults are most commonly affected.

Dyshidrotic eczema is often triggered by contact with concrete, nickel, or cobalt as well as personal care products like shampoo or soap. Stress, sweat, and heat are other potential triggers. The cause of dyshidrotic eczema is unknown but does not involve an allergic reaction.

How to Manage Dyshidrotic Eczema

Blisters caused by dyshidrotic eczema are usually managed with medicated soaks and cool compresses to dry out the blisters and ease discomfort. Moisturizers and lotions can reduce skin dryness as well as the risk of flare-ups.

Mild cases may be managed with topical corticosteroids. If your condition is severe, oral steroids or a steroid shot may be preferred.

Vesiculobullous Tinea Pedis

Vesiculobullous tinea pedis is a type of athlete’s foot that affects the inner surfaces of your feet. It is caused by an overgrowth of fungus that thrives in damp, warm environments like sweaty socks. It is called vesiculobullous because it involves vesicles (tiny fluid-filled sacs) and bullae (large blisters).

People who wear closed-toe shoes in hot, humid environments are more susceptible to this type of athlete’s foot. Other risk factors include obesity, a weakened immune system, and residing in a long-term care facility.

How to Manage Vesiculobullous Tinea Pedis

Vesiculobullous tinea pedis, like any other form of athlete’s foot, is managed with topical antifungal medications. They are applied to the skin once or twice daily for between two and four weeks, but recurrence is common.

Insect Bites

Insect bites are incredibly common and, depending on the type, can cause rash, itching, pain, redness, swelling, and blisters. Spider bites especially are known to cause a tiny but sometimes painful blister at the site of the injury. Fire ants and ticks can do the same.

How to Ease the Discomfort of Insect Bites

Insect bites usually clear on their own, but there are things you can do to help ease the discomfort:

• Use an over-the-counter (OTC) hydrocortisone cream for itching and swelling.
• Take a nonsteroidal anti-inflammatory drug like Advil (ibuprofen).
• Take an OTC antihistamine like Claritin (loratadine) to relieve swelling and itch.
• Apply an ice pack to the bite to reduce itching and swelling.

Stasis Dermatitis

Stasis dermatitis occurs when there is poor blood circulation in the lower legs. The condition develops when valves in a vein are too weak to push blood toward the heart.

Symptoms of stasis dermatitis can include:

• Swelling of the ankles
  
• Red rash or bumps that can blister and ooze
• Itching
• Dry, scaly skin
• Varicose veins
• Darkening of the skin
  
• A heavy feeling in the legs after sitting or standing

If oozing blisters are left alone, they can sometimes turn into ulcers and leave behind unsightly scars.

How to Manage Stasis Dermatitis

Compression socks can help improve circulation and prevent the pooling of blood in your legs.

Your healthcare provider may also advise you to do the following:

• Elevate the legs every two hours to reduce swelling.
• Avoid foods that are high in salt.
• Use topical corticosteroids to reduce inflammation.
• Use a topical antibiotic for minor infections.

Laser therapy can be used to unblock obstructions in veins that impede blood flow. Your healthcare provider may also recommend foam sclerotherapy, which is a procedure where a foam substance is injected into damaged veins to redirect blood flow to healthier veins.

Epidermolysis Bullosa Simplex

Epidermolysis bullosa simplex is a genetic disorder in which any minor injury or friction can cause the skin to blister. Mild cases affect the hands and feet, but severe cases can cause blisters to form all over the body, increasing the risk of infection and dehydration.

Over time, the condition can also cause the skin on the hands and feet to become hard and thick.

How to Manage Epidermolysis Bullosa Simplex

Management of epidermolysis bullosa simplex is focused on protecting the skin from any friction or injury.

Your healthcare provider may also advise the following:

• Use wound dressings to protect the skin while it heals.
• Wear soft footwear that doesn’t irritate the foot or cause friction.
• Use foot antiperspirant to reduce the risk of blistering.
• Apply topical keratolytics (medications that dissolve skin flakes and scales) to the soles of the feet to keep them from hardening.
• Use topical antibiotics for minor infections.
• Prescription medications such as Filsuvez (birch triterpenes)

Prevention

To prevent chafing that can lead to blisters:

• Always wear socks or nylons with shoes.
  
• Make sure shoes fit properly and aren’t too tight or too loose.
• Protect problem spots by applying petroleum or wearing a soft bandage or moleskin.
• See a podiatrist if you suspect you have bunions, hammertoes, or other abnormal lumps on your feet.

When breaking in new shoes, wear thick socks and/or use cushioned insoles to protect your feet. Wear the shoes for only short periods of time until they are amply softened. Tie the shoelaces tightly so your feet don't move around. Most importantly, make sure the shoes are the right size for your feet.

When to See a Healthcare Provider

Blisters on the feet can be difficult to heal, especially if you work on your feet, are an avid walker or runner, or are an athlete training for competition.

See your healthcare provider if a friction blister does not go away after two weeks or shows any signs of infection, such as:

• Foul-smelling drainage
• Increased warmth
• Pain that is severe, last for more than a week, or is not improving
• Pus (a thick white, yellowish, or green-tinged fluid)
• Redness or streaking extending from the blistered area
• Swelling
• Whole-body symptoms, such as a fever

Foot blisters accompanied by the following symptoms also warrant a visit to a healthcare provider:

• Blistering rash on other parts of your body
• Blisters of unknown cause that don't resolve in a few days
• Foot rash or blister that does not clear up after two weeks
• Leg swelling

Recurring foot blisters that appear in the same spots should be evaluated by a podiatrist. Foot blisters that return can be a sign of bunions, hammertoes, or other structural abnormalities on your feet.

People with diabetes, neuropathy, or circulatory problems need to take extra care to prevent foot infections. Examine your feet daily and see a podiatrist if you have any signs of blister growth.

Diagnosing Blisters on the Feet

Your healthcare provider will be able to diagnose your blister with an examination. If they suspect an infection, they may want to take a sample of fluid from the blister to determine how it should be managed.

Summary

Various conditions can cause blisters to form on your feet. These include excess moisture and sunburn to common skin conditions like athlete's foot, allergic contact dermatitis, eczema, and psoriasis. Less common causes include stasis dermatitis caused by poor blood circulation and a rare genetic disorder called epidermolysis bullosa simplex. Even some insect bites cause blisters.

Although the management of foot blisters varies by the underlying cause, proper foot care and hygiene are essential, irrespective of the cause.