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What Is a Vesicular Rash?

Medically Reviewed by Dan Brennan, MD on April 30, 2021

A vesicle is a small, fluid-filled blister. It can range in size from pinpoint to 5 millimeters, which is about the size of a pencil eraser. A vesicular rash occurs when there are vesicles in the area of your rash. Most vesicular rashes are harmless and will go away, but there are some serious diseases that can cause vesicular rashes. 

What Causes a Vesicular Rash?

There are many conditions that can cause a vesicular rash. Some of these include:

Physical and chemical causes. This category includes rashes that result from issues such as exposure to the elements, chemicals, or insect venom.

A heat rash develops when you have blocked pores that trap sweat under your skin. It tends to happen in hot, humid weather. In babies, the rash is usually on the neck, shoulders, and chest. In adults, it's usually in the folds of skin and places where clothing rubs. It usually goes away on its own, but severe cases may need medical care.

Chilblains are small, itchy patches that usually appear on your fingers or toes after you've been exposed to cold, but not freezing, weather. They usually appear a few hours after you've been in the cold. They usually go away on their own, but you may need to see a doctor if they don't.

Polymorphous light eruption is a rash that develops in people who have a sensitivity to the sun. It usually happens after the first sun exposure of the year, in the spring or early summer. It appears around 30 minutes after exposure to the sun, often on areas of the body that are covered in the winter, such as the arms and upper chest. It normally goes away on its own within 10 days. 

Bacterial and viral causes. Vesicular rashes that are caused by viruses and bacteria often occur with a fever. Bacterial diseases that can cause a vesicular rash include:

Viral diseases that can cause a vesicular rash include: 

Contact dermatitis.Contact dermatitis is a vesicular rash that occurs after exposure to something you're allergic to or that irritates you. Irritant contact dermatitis is the most common type. It can occur in anyone and often happens after repeated exposure. Soaps, detergents, urine, stool, saliva, and solvents are common causes of irritant dermatitis.

Allergic dermatitis occurs when you're exposed to something you're allergic to, such as poison ivy, cosmetics, food, or dye. The rash usually appears within a few hours of when you were exposed. Chronic contact dermatitis can develop into thickened, scaly skin. 

Rare causes. There are other rare diseases that can cause vesicular rashes such as autoimmune blistering diseases. These occur when your body mistakenly attacks healthy tissue. There is no cure, but these diseases can often be controlled with treatment. Without treatment, they can cause life-threatening complications.

How Is a Vesicular Rash Diagnosed?

Your doctor will listen to your symptoms and ask you questions about how and when your rash developed. They will do a physical exam and examine your rash. This may be enough for a diagnosis or you may need more tests. They may do blood tests or scrape off a bit of the skin from the rash for a biopsy.   

How Is a Vesicular Rash Treated?

The treatment for your rash will depend on the cause but may include:

Many vesicular rashes will improve on their own or with home treatment. If your rash is itchy, the following home remedies may help:

  • Take an oatmeal bath.
  • Moisturize your skin with a fragrance-free, additive-free moisturizer.
  • Apply a cold pack or cold, wet washcloth to the itchy areas.
  • Use a topical anesthetic that contains pramoxine.
  • Use a cooling lotion such as calamine or menthol.
  • Refrigerate your moisturizer for a cooling effect.

To help prevent itching, dermatologists recommend the following tips: 

  • Keep your baths and showers short, or under 10 minutes.
  • Keep your water lukewarm, not hot.
  • Use fragrance-free skincare products.
  • Avoid extreme temperatures.
  • Wear loose-fitting, comfortable clothes.
  • Reduce your stress.
WebMD Medical Reference

Sources

SOURCES:

American Academy of Allergy, Asthma, & Immunology: "CONTACT DERMATITIS OVERVIEW."

American Academy of Dermatology Association: "HOW TO RELIEVE ITCHY SKIN."

Infection and Chemotherapy: "Febrile Illness with Skin Rashes."

MAYO CLINIC: “Chilblains.”

MAYO CLINIC: "Heat rash," "Polymorphous light eruption."

National Organization for Rare Diseases: "Autoimmune Blistering Diseases.

Primary Care Dermatology Society: "Blistering (bullous) disorders - an overview."

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