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Bullae are blisters that appear when fluid is trapped under a thin layer of your skin. Learn more about what causes them, and how to treat and ...

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What Are Bullae?

Bullae are fluid-filled sacs or lesions that appear when fluid is trapped under a thin layer of your skin. Bullae are similar to blisters and vesicles, with the only difference being in size.

Vesicles are about the size of the top of a pin, reaching a maximum size of about 10 millimeters in diameter. After this point, a vesicle is considered a blister. When a blister becomes larger than 1 centimeter in diameter, it is a bulla. (Bulla is the singular form of bullae.)

What Causes Bullae?

Bullae and blisters are common occurrences that can be caused by various medical and environmental factors.


One of the most common causes of bullae is friction, such as the friction that occurs from using a shovel or other tool, or rubbing against a shoe. Friction blisters appear most often on your hands and feet.

Contact Dermatitis

If you come into contact with things that irritate your skin, like latex, cosmetics, or poison ivy, you could develop a condition called contact dermatitis. Contact dermatitis is an allergic reaction that also causes bullae.

Other Causes

Other potential causes of bullae and blisters include:

  • disorders of the skin, like impetigo
  • chickenpox
  • thermal burns, or sunburns
  • frostbite
  • trauma to your skin

Recognizing When You Have a Bullae

You should be able to tell that you have a bulla or blister simply by looking at it.

The skin that is affected will be slightly raised and have a liquid that resembles water inside. It is not recommended that you pop the bulla or remove the skin covering your bulla, though it may be tempting.

That skin acts as a protective barrier against infection. If you break the skin in order to drain your bulla, you risk allowing bacteria into the wound.

If you have an infected bulla, the normally clear liquid inside it may appear milky. If your bullae are a result of trauma, they may contain blood as well.

Treatment: Getting Relief From Your Bullae

You should see your doctor if your bulla is causing you pain or restricts your movement at all. Do not try to burst or pop your blister on your own, since this can lead to an infection.

If you have problems with your circulation or if you have diabetes, talk to your doctor before trying to treat your bulla at home.

Home Treatment

Blisters and bullae can usually heal naturally if they are left alone.

To avoid further irritation or making your bulla worse, you can put a protective bandage over the area. A gauze pad is best since the fabric absorbs moisture while still allowing your bulla to breathe.

Try not to put pressure on the area, because this could cause your bulla to burst. However, if your bulla contains blood, it should be tightly wrapped. This will stop the bleeding.

You might try over-the-counter antiseptic ointments from your local drug store to use on your blister.

Medical Treatment

If your bulla or blister needs to be drained, you should have a doctor perform the procedure. This will lower your risk of infection.

During your visit, your doctor will likely swab the area with alcohol to remove any dirt or bacteria. Then he or she will puncture your blister using a sterile needle.

After the blister has drained completely, he or she will apply a bandage with antiseptic ointment onto the area. After a few days, you may choose to remove the skin that was covering your bullae. You can sterilize scissors with alcohol and use them remove the extra skin.

Preventing Bullae and Blisters

Not all bullae and blisters can be prevented. However, some simple steps can help to keep you bulla-free.

To prevent developing a bulla as a result of friction, try placing a bandage or protective covering over the irritated area before beginning the activity.

If you play sports, there are socks available with additional padding for areas of the foot prone to blistering. You can also add fabric like moleskin to your shoes if they rub on your skin.

Written by: Carmella Wint
Edited by:
Medically Reviewed by:
Published By: Healthline Networks, Inc.
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