by Philip Alfred Brunell, M.D.
Senior Attending Physician
Clinical Center, National Institute of Health
Bethesda, Maryland

What is varicella (or chickenpox)?

Varicella, commonly referred to as chickenpox, is an infectious disease that is caused by a virus. The infection produces a rash with fluid-filled "vesicles," or lesions, on the face and body.


What causes varicella (or chickenpox)?

The disease is caused by the varicella-zoster virus, or VZV, a member of the herpes family of viruses. As the name implies, it causes varicella, or chickenpox, as well as "zoster," or shingles. After a recovery from varicella, the virus remains in some of the body's nerve cells in an inactive, or "latent," state. After many decades, the virus may become active again, travel down the nerve cells, and produce a rash on the skin. This rash is similar to the rash produced by varicella; however, the rash in zoster occurs in one segment of the skin, on one side of the body, rather than all over the body, as in varicella. Occasionally, zoster occurs in children, but it most commonly occurs in older adults.


Who gets varicella (or chickenpox)?

Varicella occurs in children. Fewer than two percent of the cases occur in adults. About half of all children will have had varicella by the time that they enter school. Varicella can occur early in infancy, and it can occur in a newborn if the mother had chickenpox just before delivery. Varicella is very contagious. If there is a case of it in a household, there is only a 1 in 25 chance that individuals in the house who are susceptible to varicella will not be infected.


How does the varicella-zoster virus cause disease?

Varicella occurs following close contact with a person who has the disease. Children are contagious the day before the rash, which suggests that they are able to spread the disease from their respiratory tract. The virus is inhaled, and then multiplies in the newly infected person. It is transported in certain blood cells to the skin, where it multiplies and causes the skin lesions, or vesicles.


What are the common findings?

The most common finding of varicella is the fluid-filled skin vesicles, usually no more than an eighth of an inch in diameter, which may have a slight redness around them. They start centrally on the body, and then spread to the arms and the legs. Often, vesicles can be felt on the scalp before they can be seen on the skin. Scabbed or crusted lesions, or a flat or slightly raised red rash, may occur at the same time as the vesicles. Often, scratch marks will result from the scratching of a very itchy rash.

The temperature is generally 100oF to 102oF. There is a cause for concern if a temperature is greater than 103oF. Fussiness may occur, caused mainly by the itching. Respiratory and gastrointestinal symptoms are not usually associated with varicella.


How is varicella (or chickenpox) diagnosed?

Varicella is diagnosed simply by looking. Laboratory testing is rarely required; although, there are tests that can be performed. Chickenpox can be confused with insect bites, hand-foot-and-mouth disease, and rickettsialpox. A history of exposure to a person with either chickenpox or shingles about two weeks previously is helpful in making an accurate diagnosis.


How is varicella (or chickenpox) treated?

Medication to treat the fever rarely is required. Aspirin or aspirin-containing medications (look for "salicylate" on the label) should never be given to children with varicella, because it has been associated with Reye's syndrome. Acetaminophen may prolong the itching. Ibuprofen has been associated with a severe, complicated streptococcal disease, but this drug may have been given for relief of the complication, rather than for treatment of varicella; therefore, it cannot be causally related.

The itching may require treatment. Calomine lotion may be applied to the skin, or the child may bathe in an oatmeal bath (Aveno). The drying of the oatmeal on the skin after the bath may offer relief. Oral medications, such as Benadryl, also are available. Since it may cause sleepiness, Benadryl is best used at bedtime. Your doctor may recommend other oral medications, if necessary.

It is very important to keep the skin clean. Daily showers or baths, preferably with an antibacterial soap, is recommended. Phisohex is excellent, but it may be too drying. Bathing will not cause the rash to spread on the skin. The scratch marks on the skin of patients with varicella do not have vesicles, meaning that an individual cannot spread the virus by inoculating it into the skin or by bathing. It is best to prevent scratch marks by trimming a child's nails.

Although acyclovir-a specific antiviral drug that inhibits the growth of VZV-has been approved for use in children, there has been little enthusiasm for it. It must be given within 24 hours after the onset of the rash to be effective. The effect on a person's symptoms is minimal; however, they are statistically significant when compared to the symptoms of a person who has not had the drug. In adolescents and adults who have more severe chickenpox than children, acyclovir may be useful. The drug may be more effective in second cases in a family, where acyclovir can be obtained at the time of the first child's illness, and treatment can be started on the other children as soon as a rash appears. Second cases tend to be more severe than the first case in a family.


What are the complications?

Most cases of varicella are mild, and can be treated by applying ointment to the skin; however, some cases may require antibiotics. Rarely, cases are very severe. If your child develops a skin infection following varicella, us should evaluate it.

The most common complication of varicella is a bacterial infection of the skin. This can occur when the fever rises after several days of illness or redness appears on the skin. The skin also may be warm and tender. In a severe infection, pain may be a prominent symptom. In recent years, streptococcal skin infections have become more frequent, and require prompt attention.

Neurologic complications do occur with varicella. The most common complication occurs 1 in about 4,000 cases, and is characterized by difficulty with balance. Although this is frightening to the child and the parents, it generally gets better by itself with time. Loss of consciousness and convulsions with fever, headache, and vomiting may indicate encephalitis. This complication occurs 1 in about 40,000 cases, but it may be life threatening. In the past, before the warning about aspirin, similar symptoms were seen in Reye's syndrome. In any of these situations, your physician should be contacted.

There are a number of less common complications that include, among others, bleeding disorders, joint involvement, and kidney problems.


How is varicella (or chickenpox) prevented?

Avoiding contact with those individuals who are affected with chickenpox can prevent it; however, this is very difficult. Many children are not even aware that they have been exposed. Protecting children from varicella is cumbersome, as they must be kept from school and other activities.

Immunization is the only practical way to prevent varicella. A live attenuated (weakened) varicella vaccine is recommended for all children who have passed their first birthday and have not had chickenpox. Children under 12 years of age require only a single injection; adolescents and adults are given two injections. The vaccine has few side effects; tenderness or pain at the injection site is the most common. Occasionally, a child may have a few chickenpox lesions on the injection side or over the trunk. The vaccine is effective in preventing or modifying varicella. In persons who have had the vaccine and still developed varicella, their cases have been extremely mild.

There are two concerns about the vaccine: how long immunity will last, and whether zoster will be a greater problem later in life in vaccinated children than in children who actually had chickenpox. There is no reason to suspect that zoster will be a problem since children who have had the vaccine do not seem to get it more frequently, and children with leukemia who were vaccinated had zoster less frequently.

Chickenpox is a much more severe disease in adults than in children. Most children will be immunized during childhood, and it is anticipated that there will be fewer cases of varicella. Therefore, children who are not immunized during childhood will have a decreased chance of contracting chickenpox as an adult. However, children who are not vaccinated will be susceptible adults, and, if infected, may get a severe case of chickenpox. If vaccine immunity should decrease, it is likely that there may be partial immunity, which will modify the severity of chickenpox in an adult who was immunized as a child. At the present time, there is no evidence to suggest that the protection produced by the vaccine will be lost.

In persons who are exposed to varicella, the antiviral drug, acyclovir, may be given. An injection of Varicella-Zoster Immune Globulin (VZIG) is used to protect adults and children who have compromised immune systems (e.g., those receiving high doses of steroids or children with leukemia), if they are exposed to chickenpox. This injection is very expensive (about $500), and it provides protection for only a few weeks. Thus, it is necessary to give it at the time of each exposure. However, many individuals will get chickenpox following an exposure of which they were unaware.


What research is being done?

Efforts continue to find better drugs to treat varicella. In addition, basic research is being conducted to better understand why the virus becomes latent and why it becomes activated to cause zoster. Currently, there is a study, which eventually will have 37,000 participants, to determine whether a stronger varicella vaccine can prevent shingles in people over 60 years of age.


Links to other information

Vaccine Information Statement for Chickenpox (Varicella)



Brunell, P.A. Varicella-Zoster (Chickenpox) in Rudolph's Pediatrics, 20th ed., Appleton and Lange, Stamford, CT, 1996.

Report of the Committee on Infectious Diseases, American Academy of Pediatrics, Elk Grove Village, IL, 1997.

Copyright 2012 Philip Alfred Brunell, M.D., All Rights Reserved