Skin infections and contact with irritating substances provoke inflammation and immune responses in the skin tissues. These responses often lead to the development of itching and eruption of fluid-filled blisters, or vesicles, in the affected skin areas. The blisters rupture and heal without scarring in most cases, and itching gradually recedes as the blisters resolve. Topical or oral treatments may help speed recovery and ease discomfort.
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Impetigo is a common, bacterial infection of the superficial skin layers. It occurs most frequently in babies and young children. Fragile, fluid-filled blisters typically develop on the face, arms or legs. Although the blisters usually itch, they are not painful. Scratching or other skin friction ruptures the initial blisters, which leak infectious fluid. Touching the fluid and then another part of the skin can lead to a secondary crops of blisters. The infection usually clears within 2 weeks. Doctors often prescribe a topical antibiotic ointment to prevent spread of the infection. Oral antibiotics may be prescribed for people with a widespread rash and those with a high risk for complications.
Herpes Simplex Infections
The herpes simplex viruses commonly infect the skin and moist surfaces of the body, causing episodic outbreaks of fluid-filled blisters. Common herpes simplex virus skin infections include cold sores, genital herpes and herpetic whitlow, a herpes infection of the fingers. Itching, tingling or burning in a localized area of the skin often signals the onset of a herpes outbreak. Tiny fluid-filled vesicles form at the site of the abnormal skin sensations. The tender vesicles often itch or burn. Rupture of the vesicles releases the highly infectious fluid contents. Although herpes simplex infections persist for life, antiviral medications may decrease the number and duration of symptomatic outbreaks.
Chickenpox and Shingles
Chickenpox and shingles are caused by the varicella-zoster virus. Initial infection with the virus causes chickenpox, which is characterized by headache, fever and a red rash that gives way to small, fluid-filled blisters that itch. There are often several crops of blisters, which most commonly appear on the trunk of the body. Although the rash associated with chickenpox eventually goes away, the virus remains in the body and can be reactivated later in life. Reactivation of the varicella-zoster virus is known as shingles. Similar to chickenpox, shingles causes an outbreak of small, fluid-filled blisters in a specific area of the body. The outbreak causes pain in the affected skin along with itching and burning. Chickenpox can be effectively prevented with a recommended childhood vaccine. A single dose of the zoster vaccine is also recommended for adults 60 and older to prevent shingles.
Contact dermatitis describes a localized skin reaction to an irritating substance. The reaction can be allergic or nonallergic. Allergic contact dermatitis is triggered by direct skin contact with an allergy-provoking substance, such as nickel, fragrances, leather, rubber and urushiol -- a plant oil produced by poison ivy, sumac and oak. With irritant contact dermatitis, the skin reaction is not due to an allergy. Common culprits include cleaning chemicals, detergents and body soaps. With both forms of contact dermatitis, the area of contact with the provoking substance typically appears red and swollen with moderate to intense itchiness. Fluid-filled blisters usually develop in the affected area. Rupture of the blisters leads to crusting and flaking. Intense inflammation may cause skin cracking and oozing. Topical steroid ointments or creams can help alleviate the discomfort of an acute case of contact dermatitis.
When To Seek Medical Care
See your doctor if you develop an unexplained blistering rash, especially if you have a fever or the rash is spreading. It's difficult to distinguish infectious from noninfectious causes of this type of rash, so it's best to see your doctor for an accurate diagnosis and treatment. Seek immediate medical care if you develop blisters larger than one-quarter inch in diameter, which could indicate a more serious medical condition.
Reviewed by: Tina M. St. John, M.D.
- American Family Physician: Impetigo: Diagnosis and Treatment
- Merck Manual Professional Version: Herpes Simplex Virus (HSV) Infections
- American Family Physician: Diagnosis and Management of Contact Dermatitis
- Merck Manual Professional Version: Chickenpox (Varicella)
- Merck Manual Professional Version: Herpes Zoster (Shingles; Acute Posterior Ganglionitis)