A bulla is a large, fluid-filled blister that can occur on the skin or inside the body. It can be caused by various factors, including burns, infections, and allergic reactions. Treatment involves protecting the blister and using medicated creams or lotions.
A bulla, bullae in the plural, is the medical term for a large, thin-walled, fluid-filled bladder. The walls of this type of blister are translucent, and the fluid inside can be lymph, blood, pus, or serum — any type of clear body fluid. A blister most commonly occurs on the skin, but can also form on the corneas and membranes that line the inside of the body, such as the mouth, nose, throat, and lungs. Common causes include insect bites, infections, burns, herpes simplex virus, and allergic skin reactions. Recommended treatments include protecting the blister with a bandage and applying medicated creams or lotions.
In Latin, bulla means bubble, pin, or knob, and the term is particularly used for a rounded protrusion that is hollow or filled with liquid. In medical terms, a blister must be greater than 0.2 inch (0.5 cm) in diameter to be called a bulla. The smallest blisters are called vesicles. A bubble formed on the membranes lining the inside of the lungs is called a bleb.
A blister often forms as a result of a skin injury such as frostbite or some type of burn, including sunburn, chemical burns, and friction burns. The herpes simplex virus commonly causes these types of blisters and is often called a cold sore. These types of blisters can also be caused by contact with certain poisonous plants and creatures, such as poison ivy and jellyfish. In some cases, more serious medical conditions such as chickenpox, thyroid disease, and lupus can also lead to blisters.
A blister can be epidermal or subepidermal, depending on whether it forms between two layers of skin or under the skin. An epidermal blister occurs when two layers of the outermost layer of skin, called the epidermis, separate and fluid is trapped between them. In the case of a subepidermal blister, there is a separation between the epidermis and the underlying skin structure, called the sub-epidermis, and fluid then fills the affected area.
To avoid pain and possible infection, the skin covering a blister should not be removed. Recommended treatments include applying an antibiotic or antiseptic cream and protecting the blister with a bandage or other form of skin dressing. Tincture of benzoin is also a recommended treatment for blisters. Home remedies such as tea tree oil, lavender oil, aloe vera gel, and petroleum jelly can also be used.
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