What Is The Liquid In A Blister?

The liquid inside a blister is a serum that leaks from adjacent tissues when your skin is injured. Serum protects the skin as long as the blister remains closed. Large blisters are referred to as bullae while small ones are called vesicles. Therefore, a blister is a pocket of liquid under the skin.

Most blisters heal after a few days without seeing a doctor. However, others need accurate diagnosis and treatment. Continue reading to find out more about causes of blisters, symptoms, treatment and prevention.

What causes blisters?

Many factors induce blisters. Here are some of them.


Repetitive rubbing of the skin causes friction that induces blisters. These blisters usually form on your hands or feet where abrasion is experienced when running, walking and hitting objects. Thick horny layers on the skin produce blisters.

Warm conditions promote the development of blisters more readily that wet and dry conditions. Damp conditions also encourage blisters. Under normal circumstances blisters are safe, and you have nothing to worry. However, in some rare cases, they can lead to severe medical conditions such as ulcerations and infections.

Extreme temperatures

Blister formation helps in classifying burns. First-degree burns cause blisters after a few days while second-degree burns cause blisters to form immediately. High temperatures are responsible for the formation of blisters.

Freezing temperatures also cause blisters. That explains why frostbites induce blisters during winter or when you hold frozen products for long. Blisters form as a defense mechanism to safeguard lower skin regions from extreme temperatures.

Exposure to chemicals

Certain chemicals can cause the skin to blister, a condition known as contact dermatitis. It occurs mostly when you come in contact with some products including:

  • Detergents
  • Nickel sulfate from electroplating
  • Chemicals used in war such as mustard gas
  • Cosmetics
  • Solvents
  • Balsam of Peru

Crush and pinch

Blood blisters form when a tiny blood vessel close to the skin surface is ruptured causing blood leakage between skin layers. Such blisters are filled with blood.


Some medications such as nalidixic acid trigger blistering of the skin. Others including doxycycline increase the chances of blisters resulting from sunburns. In extreme cases, some medications trigger life-threatening blisters to form. For instance, erythema multiforme blister disorder damages more than 30 percent of the skin.

Medical conditions

Medical conditions that can cause blisters include:

  • Dermatitis herpetiformis
  • Pemphigus
  • Cutaneous radiation syndrome
  • Chickenpox
  • Eczema
  • Bullous indigo
  • Herpes

Do blisters have symptoms?

Blister symptoms vary depending on the causes. These bubbles of liquid under the skin may be itchy, painful or show no symptoms. Blisters caused by infections have symptoms related to the type of infections. Some symptoms include:


  • Bullous impetigo forms reddened blisters that burst easily.
  • Herpes simplex type 1 virus causes tiny blisters on the lips that are itchy, reddened, tingle and swollen. Painful sores develop when the blister bursts are leaking fluid.
  • Herpes simplex type 2 blisters affect the genitals. Initially, they appear as tiny red bumps that eventually become blisters in the affected regions such as the penis, thighs, buttocks or vaginal area.
  • Varicella-zoster virus responsible for causing chickenpox begins as an itchy rash that turns into itchy blisters fast. The infection can also cause shingles that creates tiny painful blisters that form in a linear pattern.
  • Coxsackievirus commonly referred to as foot and mouth disease causes painful blisters on hands, feet and in the mouth.

Skin diseases

Some skin diseases are symptoms of blisters, primarily occurring on the hand palms, mucous membranes, feet, nose, genitals and in the mouth. These symptoms can be accompanied by painful muscles, fever, cough and sore throats.

Medication reactions

Medication reactions symptoms vary. In some instances, your skin becomes too sensitive to the sun’s rays leading to sunburn blisters forming. Severe reactions from medications affect large tissues including respiratory and digestive tract. Fever and malaise mostly accompany it.

How do blisters form?

A friction blister is the most common type experienced by many people. They develop as a result of stress between the skin surface and other parts of the body. The Stratum spinosum part of the skin is more prone to blisters than other regions. This layer tears away underlying tissues making plasma-like fluid to leak and fill the gap created. This fluid is responsible for promoting new growth and regeneration.

It takes approximately 6 hours after blister formation for underneath cells to start absorbing amino acids and nucleotides for building new proteins and DNA. After 24 hours, cell division increases and new skin layer is formed steadily. 48 hours later, the new skin can be observed, and after 120 hours a new upper layer is visible.

As new cells grow, blister fluid is reabsorbed causing the swelling to subside. Are you wondering where the pain comes from? As tissues shear deep into the skin layers, they come in contact with nerve endings that produce pain. Therefore, when you feel pain on your hand palms or feel soles, don’t worry, new skin layers are developing.

How to diagnose blisters?

Some causes of blisters remain unknown. In such cases, your doctor may ask you about your medical history including allergies and medicine you have taken in the past. You may also be asked about your family history and whether you were exposed to chemicals or allergies.

Based on blister appearance and your history, your doctor may diagnose the cause. In case allergies are suspected, the doctor may recommend patch tests to ascertain and identify the allergen. It’s also prudent to note that some blistering diseases can be diagnosed using skin biopsy. In such a case a small tissue is removed and taken to the laboratory for examination.

How to treat blisters?

Most blisters don’t need treatment to heal. As the new skin develops, blister fluids disappear slowly and will eventually dry and peel off.

Popping blisters is not advised since the liquid bubble protects underlying skin layer from infections. When removed, the wound is exposed to infections from bacterial invasion. You may cover the blister to protect it from trauma when healing.

What if the blister bursts? Desist from peeling off the dead skin on top. Instead, allow the liquid to flow naturally and wash it with soapy water. Cover the opened blister with a sterile dry dressing.

To reduce discomfort experienced, you can get over the counter medications like hydrocolloid dressings that promote healing. Similarly, allow blood blisters to heal naturally. If popped, they can be more painful than ordinary blisters. You can use ice packs to get some relief. Put a towel on the affected area then place ice packs on it to prevent direct contact with your skin.

How to prevent blisters?

Friction blisters can be easily prevented by addressing the cause of friction. You can avoid it in the following ways.

Preventing blisters on your feet

Put on well-fitting, clean and comfortable socks. Dirty, poorly fitted and stiff shoes increase your chances of developing blisters. Select socks that can manage moisture and also change them frequently.

While exercising or engaging in sporting activities wear socks designed for sports. They are made to absorb foot sweat produced. After walking or hiking, take short breaks before trekking for long.

It’s recommended to apply padding, moleskin or tape to risk spots to protect them from developing blisters. Friction management patches that are placed inside the shoes are paramount since they remain for long even if you change insoles and socks.

Preventing blisters on your hands

Wearing gloves when working with tools or doing manual work is crucial in the prevention of blisters on your hands. Even in sports like gymnastics and weightlifting, remember to tape your hand. Use talcum powder to reduce friction even when you have gloves. However, keep in mind that talcum powder absorbs moisture, therefore cannot be used for long duration exercises.

Preventing other blisters

Avoid exposing yourself to direct sun if you are under medications known to increase sun sensitivity. During cold weather conditions, put on heavy socks, hats and use mittens to safeguard your skin from chilling winds and freezing temperatures.

Try as much as you can to avoid allergens and irritants known to trigger eczema. Wash your hands frequently and don’t touch skin sores. Protect your children from sharing toys with kids with blisters from infections unless you are sure they are not transmittable.

When to call your doctor?

Call your doctor if you have unexplainable blisters that are painful or accompanied by fever and malaise. If you know the cause of a blister but it exhibits signs of infections like increased redness, oozing pus or blood and swelling, get in touch with your doctor immediately.


Most blisters disappear after a few days or weeks when the infection subsides or its cause is removed. It’s prudent to remain vigilant with blisters since some of them are signs of other infections. Stubborn or recurring blisters should not be ignored. Why risk your life or that of your loved one when you can seek medical attention?