What Can Cause Unexplained Blisters on the Feet?

A blister occurs when fluid fills a space between layers of skin. Many people get blisters from walking too much in tight shoes or by not wearing socks with shoes. While friction is responsible for many cases, blisters on the feet have other causes too, such as excessive moisture, sunburn, and allergic reactions.

Excessive Moisture

Excessive moisture can clog the pores on your feet, which can lead to small blisters. Sweating is the main cause of having excessively moist feet. This commonly occurs in runners.

Treatment

The best way to treat excessive moisture on your feet is by:

• Wearing sweat-wicking socks, such as those made of cotton, and breathable shoes like sandals
• Changing your socks or shoes when your feet become wet
• Avoiding wearing socks or shoes that trap moisture, such as socks made of merino wool and closed-toe shoes like leather boots

When blisters form on your feet because of excessive moisture, they can become more susceptible to infection. Keeping an eye on the blisters and keeping your feet dry can help avoid further complications.

Sunburn

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

Sunburn blisters take only a few hours to a day to develop and are typically painful and itchy. They present as small white bumps filled with fluid on top of the sunburned skin. The area around the blister may also be red and swollen if your sunburn is severe.

Treatment

Blisters that form because of a sunburn usually heal on their own, but there are ways you can speed up your recovery and prevent them from getting worse, including:

• Allow blisters to heal: Do not pop or pick at the blisters since this can lead to infection.
• Use cooling techniques: A cold compress or quick cool shower or bath can help relieve the painful burning sensations associated with sunburn blisters.
• Take pain relievers: If the pain is too much to bear, over-the-counter pain relievers such as ibuprofen can help.
• Use aloe gel: Aloe has long been considered a helpful tool in relieving the pain of sunburns, and it's safe to use on blisters. Just be sure the blisters are not popped or broken before applying.
• Avoid the sun: While your burn is healing, it’s best to avoid the sun as much as possible. If you can’t, wear protective clothing. Sunscreen can be used only after the blisters have healed.
• Hydrate: Drinking lots of water can help you avoid dehydration after a severe sunburn.

Allergic Reaction

Contact with an allergen, such as poison ivy, latex, or certain types of metal, can trigger an immune response. This can lead to a skin reaction and blisters. This condition is called allergic contact dermatitis.

Treatment

The best way to prevent an allergic reaction that causes blisters is to avoid allergens, but that isn’t always possible. If contact dermatitis does occur, treatment usually involves topical corticosteroid medications to alleviate the inflammation and itching. Severe cases may need to be treated with oral steroids like prednisone.

Psoriasis

Psoriasis is an autoimmune condition that causes itchy and scaly red patches on the skin. Although these patches tend to appear on the knees, elbows, torso, and scalp, they can also develop on your feet.

Psoriasis occurs because the immune system is overactive and speeds up skin cell growth. Normal skin cells grow and shed in a month. In psoriasis, skin cells do this in only three to four days. Instead of shedding, skin cells pile up on the surface of the skin, forming plaques and scales.

A rare form of psoriasis, known as pustular psoriasis, can cause white or yellow blisters. These blisters are also known as pustules. They are filled with pus made up of white blood cells. When the condition affects the feet, it is called palmoplantar pustular psoriasis.

Treatment

The main courses of treatment for the condition include:

• Oral retinoid therapy, which can slow skin cell growth and reduce redness and swelling
• Phototherapy, which uses ultraviolet light to suppress an overactive immune system and slow skin cell growth
• Topical corticosteroids to alleviate inflammation and itching
• Medications to modify the immune system reaction, like a calcineurin inhibitor

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Dyshidrotic Eczema

Dyshidrotic eczema can cause blisters on the soles of your feet, although it typically causes blisters on your hands and fingers. It causes recurrent flare-ups of blisters and comes on suddenly. The blisters caused by this condition resemble tapioca pudding. Research has shown that dyshidrotic eczema is most commonly found in young adults.

With a dermatologist's help, you can find out what triggers your blisters and avoid them to prevent flare-ups. Common triggers include personal care products like shampoo or soap. Coming into contact with nickel or cobalt can also lead to blisters. Stress, sweat, and rising temperatures can be potential triggers as well.

Treatment

Treatment for dyshidrotic eczema focuses on the treatment of the blisters as well as long-term management. Your dermatologist may recommend medicated soaks and cool compresses to dry out your blisters. You will apply these two to four times a day for 15 minutes at a time.

Dyshidrotic eczema can make your skin extremely dry. To reduce dryness and decrease flare-ups, your dermatologist will recommend a moisturizer or barrier repair cream.

Mild cases are usually treated with topical corticosteroids. If your condition is severe, corticosteroids will need to be administered orally or via injection into a muscle.  

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 results from excessive moisture on the feet.

It causes small fluid-filled blisters that can end up merging together to form one large bullae, which is a large blister with fluid inside. People who wear closed-toe shoes in hot and humid environments are more susceptible to this type of athlete’s foot. Other risk factors for vesiculobullous tinea pedis include:

• Frequent use of public showers and changing rooms
• Obesity
• A weakened immune system
• Occupations in industries that require the use of industrial-style footwear
• Residence in long-term care facilities

Treatment

Athlete’s foot is usually treated with antifungal medications. They are applied directly onto your skin once or twice a day to help clear up the fungus causing the blisters. Typically, treatment lasts between two and four weeks, and most cases clear up entirely within that time.

In some cases, the overgrowth of fungus can spread to other areas of the body such as the hands and torso. Treating it quickly can help avoid this spread.

Insect Bites

Insect bites are incredibly common, and anyone can be bitten by an insect. Different types of insect bites will cause different symptoms, which can include:

• Blisters
• Intense itchiness
• Redness and swelling
• Pain at the bite site

In some cases, getting bitten by an insect can lead to infection if the bug carries certain bacteria. For instance, ticks carry the type of bacteria that causes Lyme disease. Other complications that can occur after an insect bite include:

• A severe allergic reaction
• Hives
• Viral infections if the insect carries a virus
• Parasitic infection if the insect carries and passes on a parasite

Treatment

Insect bite symptoms usually go away on their own in time, but there are things you can do to ease the discomfort while you wait for the bite to heal. You can:

• Take over-the-counter painkillers such as acetaminophen (Tylenol) or ibuprofen (Advil).
• Apply an ice pack to reduce itching and swelling.
• Use over-the-counter anti-itch creams such as hydrocortisone.
• Take oral antihistamines to reduce the itching.

To prevent an insect bite in the first place, you can use different insect repellents when you are headed out to areas with a lot of insects, such as wooded areas.

Stasis Dermatitis

Stasis dermatitis occurs when there is poor blood circulation in your lower legs. The condition develops when the part of the vein known as the valve becomes too weak to push blood back up the legs toward the heart. Symptoms of stasis dermatitis can include:

• Swelling in the ankles
• Orange-brown discolored spots on the legs
• Redness that may appear brown, purple, or gray depending on your skin tone
• Itchiness
• Scaling of the skin on the legs
• Dry skin on the legs
• Heavy feeling in the legs after sitting or standing for prolonged periods of time
• Shiny skin

When the condition is not treated promptly, it can spread to areas other than the calves and ankles. Bleeding or oozing ulcers, which are open sores, will also form on the lower legs or on the tops of the feet if the condition isn’t treated, leaving scars after they have healed.

Treatment

Early treatment of stasis dermatitis is important to avoid permanent skin damage. Typically, treatment will begin with compression therapy, such as wearing compression socks to improve circulation in your legs. Compression socks work by gently pushing the blood from the lower leg up toward the heart.

Other treatment options may include:

• Elevating the legs over the heart every two hours to help reduce swelling in the legs
• Avoiding foods that contain high amounts of salt
• Using topical corticosteroid creams to reduce inflammation
• Taking an antibiotic if an infection occurs

Another form of treatment known as laser therapy is used to help improve the function of the veins and improve circulation by applying heat to the area to break down the veins that are causing the issue.

In some cases, ultrasound-guided foam sclerotherapy is also used to help break down veins with a foam substance that is injected into the damaged veins. Once the veins are gone, the blood in the legs will flow through healthier veins instead.

Epidermolysis Bullosa Simplex

Epidermolysis bullosa simplex is a genetic disorder in which any minor injury or friction to your skin can lead to blisters. Mild cases affect the hands and feet, but severe cases can cause blisters to form all over the body, which can leave a person more susceptible to infections and dehydration.

Typically, blistering of the skin is the only symptom that occurs with a mild case of epidermolysis bullosa simplex. Later on in life, the skin on the hands and soles of the feet can harden and become thick.

Treatment

Treatment focuses on protecting your skin from any friction or injury that can lead to blisters by:

• Using wound dressings that can help keep your skin safe from further damage while it heals
• Wearing footwear that doesn’t irritate the blisters or cause further friction on the skin of the feet 
• Using antibiotics if an infection occurs

Your doctor may recommend using keratolytics to avoid skin hardening on the hands and feet and aluminum chloride on your feet and hands to help reduce blistering. If you have issues walking because of blisters, you may need physical therapy.

How to Ease the Discomfort

To ease the discomfort of blisters on the feet, you can:

• Wash the area with mild soap.
• Use an antibacterial cream or ointment to reduce the risk of developing an infection.
• Cover the blisters with a bandage or some gauze to keep them protected.

If the blister is itchy, avoid scratching as this can cause the blister to pop. Using a cold compress or an anti-itch cream may help ease the itchiness and pain.

Summary

Various conditions can cause blisters to form on your feet, from excessive moisture or a sunburn on your feet to different forms of eczema and a rare genetic disorder like epidermolysis bullosa simplex.

While treating the underlying condition that's causing your blisters, you can ease the discomfort by washing them with a mild soap and covering them with a bandage or gauze to protect them. Resist the urge to scratch your blisters because breaking them can potentially lead to an infection.

Frequently Asked Questions

How do you treat pustular psoriasis?

In some cases, phototherapy may be used to help relieve the pain and itchiness. Immune system–modulating medications may also be used, as well as oral retinoids and corticosteroids.

How rare is pustular psoriasis?

Pustular psoriasis is an incredibly rare disease. Although the incidence in the general population is not clear, it’s estimated that roughly 3% of people with psoriasis have pustular psoriasis.

How long does it take for dyshidrosis to go away?

Although there is no cure for dyshidrosis, getting adequate treatment can help clear up and reduce flare-ups. With the proper treatment, the condition usually improves within two to four weeks. If it doesn’t by that time, further testing and other treatment options will be explored.