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Chickenpox: Causes, Symptoms, Diagnosis and Treatment

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Chickenpox, also known as varicella, is a viral infection that typically causes a rash covering large areas of the skin.


The rash starts as small, red spots and progresses to itchy, fluid-filled blisters. These blisters eventually form a scab and heal, typically within a week or two.

    Chickenpox is highly contagious and can spread quickly from an infected person to others, even without close personal contact.

    While it typically affects children, chickenpox can also spread to adults who haven’t previously had the infection or the chickenpox vaccine. Adults are at higher risk for complications from chickenpox.

    Before vaccination for chickenpox became routine in the United States, nearly everyone got chickenpox before adulthood. Since that time, cases of chickenpox and related hospitalizations have dropped dramatically.

    While you can reduce your risk of catching chickenpox by avoiding contact with people known to be infected, the most effective way to prevent the disease is to get vaccinated.

    If you suspect that you or your child has chickenpox, it’s a good idea to see a doctor. Your doctor can make a diagnosis and prescribe any necessary treatments.

    While serious complications of chickenpox are rare, it’s possible for the disease to cause more dangerous secondary infections, brain damage, or even death.

    Infants, adolescents, adults, pregnant women, and people with a weakened immune system are at highest risk for chickenpox complications.

    Signs and Symptoms of Chickenpox

    The main sign of chickenpox is a rash, consisting of itchy, fluid-filled blisters over red spots that cover large areas of the skin. This rash may start on the chest, back, or face before spreading to other areas.

    After about a week, chickenpox blisters typically develop a crust and turn into scabs.

    Other common symptoms associated with chickenpox include:
    • Fever
    • Fatigue
    • Headache
    • Reduced appetite
    These symptoms may start a day or two before the rash develops. If you develop these symptoms and know that you’ve been exposed to chickenpox, it’s a good idea to stay home to avoid infecting others.

    Causes and Risk Factors of Chickenpox

    Chickenpox is caused by a virus called the varicella-zoster virus (VZV). It’s also known as human herpes virus 3 (HHV-3), or as just the varicella or zoster virus.

    Chickenpox is highly contagious and can be spread in a few different ways:

    • By breathing in drops of moisture containing the chickenpox virus
    • Through direct contact with a chickenpox rash
    • From a pregnant woman to her fetus
    • You’re at high risk for chickenpox in these situations only if you’ve never had the disease, or if you haven’t been vaccinated for it. Either having the disease or getting vaccinated usually gives you immunity for life.

    Most people get chickenpox through close contact with someone else who has the infection. Chickenpox is contagious starting one to two days before a rash develops.

    It’s also possible to get chickenpox from someone with shingles (herpes zoster), a viral infection that occurs when the chickenpox virus, which remains dormant (inactive) in the body after the illness has resolved, reactivates later in life, causing a blistering rash that can be extremely painful.

    In the rare situation that you’ve been vaccinated for chickenpox but still get the disease, you can pass on your infection to other people — despite the likelihood that your symptoms will be mild.

    There have been cases in which someone gets chickenpox more than once, but this is extremely rare.

    How Is Chickenpox Diagnosed?

    The rash caused by chickenpox is usually enough for a doctor to diagnose it.

    If there is any doubt about what is causing your rash, your doctor can take a sample from a blister for a laboratory test. A blood test may also be an option.

    Prognosis of Chickenpox

    Most children under age 12 recover from chickenpox without any severe symptoms or complications.

    The chickenpox vaccine also prevents almost all severe illness associated with the disease. If you or your child develops chickenpox after being vaccinated, it is likely to be a mild illness.

    Certain people are at higher risk for developing severe symptoms and complications of chickenpox. This group includes:

    • Adolescents
    • Adults, especially smokers
    • Pregnant women
    • Newborns and infants whose mother never had chickenpox or the vaccine
    • People with an impaired immune system (due to a health condition or medical treatment)
    • People who take steroid medication, including children with asthma

    Duration of Chickenpox

    Once you’re exposed to the chickenpox virus, it usually takes 10 to 21 days for you to develop a rash or any other symptoms.

    The itchy rash that chickenpox causes typically lasts 5 to 10 days, before the blisters turn into scabs. Most scabs heal within 20 days of the start of a chickenpox rash.

    If you’ve been infected with the chickenpox virus, you can spread the disease to other people during the period starting one to two days before you develop a rash, and ending when all of your chickenpox blisters have formed a crust.

    While the symptoms of chickenpox clear up in two or three weeks, the virus itself stays in a person’s body for the rest of their life. For the most part, the virus remains dormant, or inactive.

    But sometimes, especially in older adults, the dormant virus becomes active again, causing the symptoms of shingles. Older adults can greatly reduce this risk by getting one of the two available shingles vaccines.

    Treatment and Medication Options for Chickenpox

    For most mild cases of chickenpox, resting, staying home, and employing some home remedies or over-the-counter products to ease the itching and discomfort are all that’s needed.

    Adults and children at risk of complications may be prescribed antiviral drugs to reduce the severity and duration of chickenpox symptoms.

    No one should take aspirin while they have chickenpox. Doing so raises the risk of developing Reye's syndrome, a serious disease that causes swelling of the brain and liver. Taking ibuprofen (Advil, Motrin) is also not recommended because it has been associated with severe bacterial skin infections.

    Medication Options

    Most of the time, no medications are needed to treat chickenpox. If you or your child has severe itching, talk to your doctor about taking an antihistamine to help control it.

    If you or your child has a fever due to chickenpox, taking acetaminophen (Tylenol) can help lower it.

    For people with an elevated risk of complications from chickenpox, doctors often prescribe an antiviral drug, such as acyclovir (Zovirax, Sitavig). This may be recommended if you:

    Other antiviral drugs that may be options for some people include valacyclovir (Valtrex) and famciclovir (Famvir).

    Another treatment option for people exposed to chickenpox is IV immune globulin (Privigen) and consists of antibodies to the virus. It may be given if you:

    Alternative and Complementary Therapies

    For most people, the only treatments needed for chickenpox are measures to relieve discomfort and help prevent bacterial skin infections. There are a number of tried-and-true home remedies, including:

    • Calamine lotion (dabbed on itchy spots)
    • Baking soda or oatmeal baths
    • Wet compresses
    • A cool bath with added baking soda, aluminum acetate, uncooked oatmeal, or a colloidal oatmeal preparation may help relieve itching from chickenpox.

    A wet compress — soaking a towel with cold water, placing it over an ice pack if desired, and holding or wrapping it against the skin — may also help relieve itching.

    Prevention of Chickenpox

    Getting the chickenpox vaccine is the best way to prevent chickenpox. This vaccine is recommended for all people who have never had chickenpox.

    Two doses of the chickenpox vaccine are needed for effective protection. Most people who receive the vaccine will never develop chickenpox, but those who do tend to have very mild symptoms — such as red spots without blisters and little to no fever.

    The chickenpox vaccine may also be given after exposure to chickenpox but before symptoms develop, and may help prevent an infection or lead to milder symptoms.

    Since widespread vaccination was introduced in the United States in the 1990s, chickenpox cases, hospitalizations, and deaths have fallen by over 90 percent.

    If you haven’t had chickenpox or the vaccine, avoid contact with anyone known to have chickenpox. Talk to your doctor if you believe you may have been exposed to someone with chickenpox in this situation.

    Complications of Chickenpox

    Complications from chickenpox are uncommon in previously healthy people, and range from mild secondary skin infections to life-threatening brain swelling.

    Among the possible complications of chickenpox are
    • Bacterial infection (usually affects skin and soft tissues)
    • Pneumonia (lung infection)
    • Brain infection or inflammation (encephalitis)
    • Liver inflammation
    • Dehydration
    • Bleeding problems
    • Sepsis (inflammatory response to infection)
    • Reye’s syndrome, in people who take aspirin (a potentially dangerous drug for someone with chickenpox)
    The people at highest risk of developing serious complications include infants, teenagers, adults, pregnant women, people with an impaired immune system, and people who take steroid drugs. But even healthy children can develop complications of chickenpox.

    While some chickenpox complications are avoidable — for example, not scratching chickenpox blisters reduces the likelihood of skin infections — some are harder to prevent.

    The best way to avoid chickenpox complications is to see a doctor for diagnosis and treatment advice if you or your child develops symptoms of chickenpox.

    If a pregnant woman gets chickenpox early in her pregnancy, this can cause a number of problems in her newborn, such as:

    • Low birth weight
    • Birth defects
    • Limb abnormalities
    In these cases, the newborn won’t actually be born with chickenpox. But if a woman develops chickenpox right before or after giving birth, it can spread to her newborn and cause a severe, life-threatening infection.

    Related Conditions

    The chickenpox virus is a close relative of herpes simplex viruses (HSV), which cause both cold sores and genital herpes. However, herpes simplex viruses do not cause chickenpox, and varicella-zoster virus does not cause the sores typical of herpes simplex infections.

    In everyone who develops chickenpox, once the infection has passed, the chickenpox virus remains dormant (inactive) in the body. But the virus can reactivate later in life, causing shingles.

    Shingles is marked by a painful rash, usually on one side of the torso. It can also occur on the neck, face, or anywhere else on the body.

    In addition to the rash — which may form blisters that itch, similar to chickenpox — shingles may cause fever, headache, sensitivity to light, or fatigue.

    When Adults Get Chickenpox

    Chickenpox is most often thought of as a childhood disease, but adults who didn’t have the disease as a child or receive the chickenpox vaccine can still get it if they’re exposed to the virus — either from someone with chickenpox or from someone with shingles.

    Adults are at higher risk for complications of chickenpox, particularly pneumonia, so any adult with symptoms of chickenpox should see a doctor for advice on treatment and preventing complications, or at least catching them early.

    Some adults may be advised to get the chickenpox vaccine even after exposure to the virus, to prevent the infection or make it less severe.

    Adults may also be prescribed antiviral drugs to help prevent chickenpox complications.

    Why Is It Called Chickenpox?

    It’s unknown exactly how the term “chickenpox” came to describe the disease in English. There’s no similar term used for the disease in other languages.

    But the term has been around for a long time, with the oldest recorded use happening in the 1600s.

    One theory for how the term “chickenpox” came to be used is that the disease was thought to be a milder version of smallpox, a serious infectious disease that was declared eradicated by the World Health Assembly in 1980. In this sense, “chicken” means weak or timid.

    It’s also possible that people thought the disease’s blisters looked like the marks from being pecked by chickens.

    Finally, the “chicken” part of the term could have morphed from an Old English word, giccin, which means “itching.”

    “Pox” refers to marks on the skin, such as the blisters seen in chickenpox.

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