Complications of chickenpox 

Chickenpox is usually mild and passes without causing any serious problems, particularly in children.

But sometimes complications can occur.

These are more common in:

• pregnant women
• adults, especially those who smoke
• newborn babies under four weeks old
• people with a weakened immune system (the body's defence system), such as people with HIV, those taking high doses of steroid medication and those having chemotherapy

Some of the main risks associated with chickenpox are outlined below.

Skin infections

The most common complication of chickenpox is the skin becoming infected with bacteria. This is more likely to happen if you or your child scratches your spots.

The skin may be infected if it becomes:

• red
• swollen
• painful and tender

Contact your GP if you think your or your child's blisters have become infected. You may need antibiotics to treat the infection.

Lung infections

Occasionally, the chickenpox virus can spread to the lungs and cause pneumonia.

This is more common in adults (particularly those who smoke), pregnant women and people with weakened immune systems.

Symptoms of pneumonia can include:

• a persistent cough
• difficulty breathing
• chest pain
• sweating and shivering

Contact your GP as soon as possible if you think you or your child may have developed pneumonia. You may need to be treated in hospital.

Infections of the brain or nerves

In rare cases, chickenpox can lead to more serious infections of the brain and spinal cord in children, people with weakened immune systems and pregnant women.

This can cause:

• a lack of energy
• drowsiness
• confusion
• seizures (fits)
• vomiting
• severe headaches
• a stiff neck
• behavioural changes
• problems with walking, balance or speech

Seek medical advice as soon as possible if you or your child develops any of these symptoms after having chickenpox. Treatment in hospital will usually be needed.

Pregnancy problems

If you become infected with chickenpox for the first time while you're pregnant, there is a small risk of potentially serious complications affecting your baby.

The risks depend on when you pick up the infection.

• Infection during the first 28 weeks can result in a rare but serious condition called congenital varicella syndrome, which may cause shortened limbs, vision problems (such as cataracts), brain damage and scarring.
• Infection during weeks 28 to 37 can mean your baby is at risk of developing shingles at some point after they're born.
• Infection a week before to a week after birth can mean your baby is a risk of a severe and potentially life-threatening chickenpox infection.

Contact your GP as soon as possible if you're pregnant or have given birth recently and you think you have chickenpox or have been exposed to someone with the infection.

Your GP can do a blood test to check if you're already immune to the infection and can arrange for you to have stronger treatments to prevent a severe infection.