Vesicles are small fluid-filled sacs or blisters that can appear on your skin. The fluid inside these sacs may be clear, white, yellow, or mixed with blood.

Vesicles are fluid-filled lesions less than 5 mm (1/2 cm). If the fluid-filled lesion is greater than 0.5 mm, it’s called a bulla. Blisters are either vesicles or bulla, depending on the size.

Blisters can be a symptom of a medical issue or a sign of tissue injury.

In anatomy, vesicles may refer to any pouch-like structure in the body. The function of these types of vesicles is to store and transport materials and waste.

Vesicles develop when fluid becomes trapped under the epidermis, the top layer of your skin. A number of different health conditions can cause them. Some of these conditions are minor, like contact dermatitis or cold sores, and don’t require medical attention.

But other causes are more serious and can signal a complicated medical issue that needs ongoing treatment. These issues may include bacterial or viral infection, autoimmune disease, and a sensitivity or allergy to medication, among others.

Causes of acute (short-lasting) vesicles on the skin include:

Causes of chronic blistering rashes include:

If you experience unexplained blistering rashes, acute or chronic, it’s best to see a doctor for a diagnosis.

Vesicles caused by burns, infections, and reactions to medication can be serious and should be treated by a doctor.

If you experience blistering of the mucous membranes of the mouth, eyes, or vagina, this may be a sign of a potentially life-threatening reaction to a drug. Seek emergency medical care.

Doctors can recognize vesicles based on their bubble-like appearance. Most develop on the surface of the skin and cause it to swell with fluid. The skin around a vesicle keeps the fluid contained.

Some blister-like lesions can rupture easily. This causes fluid to leak from the blister. When the fluid dries, it may turn yellow or crusty.

Symptoms that may occur with a blistering rash include:

  • itching
  • tenderness
  • warmth at the affected skin
  • pain
  • possible oozing

The following symptoms may occur with blistering rashes:

  • fever
  • chills
  • swollen lymph nodes
  • joint pain
  • muscle weakness or muscle ache

Vesicles or blisters can occur with a rash, known as a vesicular rash.

Some common vesicular rashes include:

  • Heat rash: Heat rashes tend to occur in hot, humid, or tropic climates. It’s caused by blockage and swelling of the sweat ducts and is usually found on the torso.
  • Infections: Bacterial or viral infections can cause rashes along with superficial vesicles or bullae.
  • Contact dermatitis: Contact dermatitis is a common cause of vesicular rash can occur after exposure to an allergen or irritant. You may develop this type of rash from poison oak or poison ivy or from touching something you might be allergic to, like substances in soap, perfume, or jewelry.

Vesicular rashes may spread quickly. In the case of viral and bacterial infections, keep the rash clean to prevent it from spreading to other parts of the body.

You should make an appointment with a doctor if you develop unexplained vesicles on your skin. If you don’t already have a doctor, try the Healthline FindCare tool to see the options available in your area.

During the visit, they’ll ask you about your recent health history and about any medical conditions that might be related to the vesicles, like other symptoms including fever, chills, itching, or pain.

They may also ask if you’ve traveled recently or had possible contact with poison ivy or sumac. They might also want to know if you’ve started any new medications or had changes made to existing ones. Finally, they may ask if you have any family history or personal history of autoimmune diseases.

They’ll also examine your skin. Your doctor may be able to diagnose the cause of your vesicles based on this information alone.

If your doctor is uncertain about a diagnosis, they may recommend more tests. They may also take a sample of fluid or a biopsy of the skin tissue from the vesicle to send to a lab. The analysis of the sample will help them to confirm a diagnosis.

Talk with a doctor about the best treatment options to reduce your symptoms.

Treatment for your vesicles depends on the cause. Over-the-counter (OTC) remedies may be enough to treat vesicles resulting from an allergic reaction, dermatitis, poison ivy, or cold sores. Many of these remedies are topical ointments that can soothe the skin. Antihistamines may be able to reduce allergy-related symptoms.

Vesicles can be accompanied by other serious symptoms, like inflammation or infection. In these cases, your doctor may prescribe medications to treat the underlying causes.

For example, bullous pemphigoid — a type of autoimmune disorder that affects older adults — is typically treated with oral steroids to help reduce inflammation and possibly immunosuppressants or monoclonal antibodies.

Bacterial infections are typically treated with oral antibiotics so as not to aggravate the vesicles.

Vesicles caused by eczema are often treated with topical medications, including topical steroids and glucocorticoids.

Burn blisters will be treated with prescription burn creams. You may also be prescribed oral antibiotics to reduce the chance of infection.

Home treatments, including alternative remedies can often be effective for treating vesicles or blisters.

According to the American Academy of Dermatology Association, you should care for an open or torn blister by washing the area with soap and water and then applying petroleum jelly. You can also use an OTC antibiotic ointment to help prevent infection. Cover the area with a clean, loose bandage to protect it.

Popping a vesicle isn’t typically advised. This can leave the area open to infection and make it take longer to heal. Unless the vesicle becomes large and exceptionally painful, leaving it alone is best. Most blisters heal on their own in 1 to 2 weeks.

Your outlook depends on the underlying cause. If your vesicles are caused by an allergic reaction or contact dermatitis, you’ll typically make a full recovery after treatment.

More serious cases of vesicles can be a result of your genetics or an infection with a virus, so the vesicles may reoccur throughout your life. Proper treatment may relieve your symptoms. But if you have a chronic condition, the vesicles are likely to return.

If you know you have allergies, you can help prevent vesicles by avoiding allergy triggers.

Herpes and cold sores are contagious, so you should also take care not to share cups, straws, or lip products. This precaution may also help prevent you from catching other viral illnesses.

Try not to wear tight-fitting clothing that rubs uncomfortably on the skin, especially in hot or damp weather. Opt for clothing that breathes, like cotton. You should wear proper attire for sports or physical activity, like socks with extra padding, to prevent friction. Moisture-wicking clothing can also be helpful. If you experience pain or redness, stop the activity.

Keep your skin clean, maintain good hygiene, and avoid irritants that could aggravate your skin. Using unscented products can help prevent rashes, as those with scents can irritate sensitive skin more.

Antibacterial soaps can help prevent infections from causing vesicles (and vesicles from becoming infected). Shower immediately after working out or coming into contact with a potential skin irritant.

In some instances, it may not be possible to prevent vesicles.

Most vesicles, blisters, and bullae can be treated with OTC treatments and home remedies. But in some cases, it’s a good idea to call your doctor.

If you experience a rapid spread of vesicles, especially with a rash, and symptoms like shortness of breath, pain, or dizziness, you may be having an allergic reaction to medications. In these cases, you should seek immediate medical attention.