What Is the Chickenpox Rash?

Here's everything you want to know about the chickenpox

pregnant woman holding a little girl with chickenpox
What do you need to know about chickenpox. Istockphoto.com/Stock Photo©-dmit

The chickenpox rash is a highly contagious infection that's caused by the varicella-zoster virus. It triggers small, red, itchy spots to appear on the body. The word "chickenpox" comes from the Old English word "gican" (meaning "to itch") or from the Old French word "chiche-pois" for chickpea, a description of the size of the lesion.

Who Gets the Chickenpox Rash and When?

The chickenpox rash is a disease of childhood—90% of cases occur in kids ages 14 and younger.

  Before widespread vaccination against this particular virus, the incidence of chickenpox in the United States approached the annual birth rate, averaging between 3.1 and 3.8 million cases per year. Chickenpox can occur at any time of the year but occurs most often in March, April, and May in temperate climates. 

Spread of the Chickenpox Virus 

The chickenpox rash is acquired by either direct contact with fluid from an infected blister or by the inhalation of respiratory droplets. For instance, when a person with chickenpox coughs or sneezes, he or she expels tiny droplets that carry the varicella-zoster virus. When a person who has never been exposed to chickenpox inhales these droplets and the virus enters the lungs, it's then carried through the bloodstream to the skin, where it causes a rash.

Common Symptoms of Chickenpox 

While the virus is in the bloodstream (before the rash begins), it causes typical viral symptoms like fever, fatigue, joint pains, headache, and swollen glands.

These symptoms usually resolve by the time the rash develops. The incubation period of chickenpox averages 14 days, with a range of nine to 21 days.

As for the skin: The chickenpox rash begins on the torso and spreads to the face and extremities. A chickenpox lesion starts as a 2- to 4-millimeter red papule, which develops an irregular outline.

A thin-walled, clear vesicle develops on top of the area of redness, making it look like a "dew drop on a rose petal." After about eight to 12 hours, the fluid in the vesicle gets cloudy and the vesicle breaks, leaving a crust.

The fluid is highly contagious, but once the lesion crusts over, it is not considered contagious. The crust usually falls off after seven days, sometimes leaving a crater-like scar. Although one lesion goes through this cycle—from the first appearance to crusting—in about seven days, another hallmark of chickenpox is the fact that new lesions crop up every day for several days. Doctors generally advise that children stay home from school until all lesions have crusted over.

How Chickenpox Is Diagnosed

A diagnosis of the chickenpox rash is usually based on the history of viral symptoms and the characteristic appearance of the rash. However, sometimes the chickenpox rash can be confused with herpes simplex, impetigo, insect bites, or scabies. Sometimes a viral culture is performed to confirm the diagnosis, but it typically takes anywhere from one to 14 days to get results.

Severity of the Infection and Rash

The number of chickenpox lesions that a person gets varies considerably.

The typical range is 100 to 300 lesions. Usually, older children and adults develop more lesions than younger children. Also, cases of chickenpox that are acquired from contact with household members are typically more severe than those acquired from community contact. People who have previously traumatized skin, such as from a sunburn or eczema, may also develop a more extensive rash. In addition to affecting the skin, the chickenpox rash can also cause lesions on the mucous membranes in the eyes, mouth, and vagina.