Chicken pox is a very common illness usually affecting children. It is caused by a virus called Varicella zoster. It occurs in clusters throughout the year. The virus spreads mainly by droplets released from the nose and mouth by sneezing. Other people will breathe in these tiny droplets. If they are not immune to chickenpox the infection develops in the nose and throat before spreading to the rest of the body. The incubation period is between 10 and 21 days, which means that susceptible people will develop the symptoms of the illness about 2-3 weeks after contact with someone with chickenpox. A person incubating chicken pox is infectious from 2 days before the first spots appear until the last spot has crusted over.

Chickenpox is a self limiting illness

The illness usually starts with a fever for about 3 days and this is accompanied after a day or two by a characteristic rash affecting first the trunk and then spreading to the rest of the body. This starts as itchy red spots which gradually fill with a clear fluid to form blisters. The fluids becomes cloudy and then the blister crust over. The scabs fall off within 10 days. The rash comes in crops so that clear blisters are seen next to older spots that have turned cloudy or crusted over. The spots can be very itchy; try not to scratch them as this can introduce infection under the skin or cause scarring. Clip your nails and keep your hands clean. Chickenpox symptoms in adults may be more severe than in children. The infection settles after about 7-10 days and usually needs no specific treatment.

Treating the symptoms

Paracetamol will help to reduce the fever symptoms. Cool baths and calamine lotion may help with the itching. If necessary a sedative antihistamine such as chlorpheniramine (Piriton) which is available over the counter from the chemist may help with itching and sleep at night. Most patients do not need to see the doctor; coming to the surgery with chicken pox just risks spreading it to other people. Children with chicken pox should stay away from school until the last spot has crusted over when they are no longer infectious (about 1 week after the first spots appear). Similar advice applies to adults; stay at home to minimise spread to other people.

Some patients may need antiviral treatment

In patients who have poor defences against infection because of treatment with steroid tablets, chemotherapy or conditions such as leukaemia, the disease may be severe. Patients with widespread eczema can also develop severe chickenpox. These patients need to see the doctor to discuss whether antiviral treatment is necessary.

One attack of chickenpox gives protection against the disease for life. It is very unusual to have two episodes of chicken pox. However, shingles, another form of the disease caused by the same virus, may occur later in life.

Chickenpox and pregnancy

85% of women have antibodies to the chickenpox virus and therefore their baby is not at risk of chickenpox even of the mother develops shingles (a reactivation of dormant chickenpox virus) during pregnancy.

In the non-immune pregnant woman, chickenpox is a potentially dangerous disease that may infect the baby and cause abnormalities. Approximately 3 out of every 1000 women who are pregnant catch chickenpox. Before 11 weeks of pregnancy there is a high chance of passing the infection to the foetus. Of these, most will develop congenital defects, mainly limb deformities, heart defects, deafness and cataracts (eye lens opacities). The risk of congenital defects drops as pregnancy advances until at 36 weeks the risk to the baby is zero. However, chickenpox in late pregnancy carries the risk of the baby developing chicken pox soon after birth, and again, non-immune mothers who are exposed to chicken pox towards the end of pregnancy should also receive protective antibodies, some of which will be passed on to the baby through the placenta.

Pregnant women who have been in contact with chickenpox, should ask the doctor for an urgent blood test to determine their immunity. Those that are not immune to the chickenpox virus will be offered chicken pox antibodies as a vaccine to prevent development of the infection. This should be given within 7 days of exposure to ensure effectiveness in preventing spread of infection to the baby.

If the mother develops chickenpox a few days before or after delivery, antibodies would also be given to the new baby for protection. Nursing mothers who develop chickenpox should consult either the midwife or doctor for further advice regarding breast feeding and handling of their baby.

Complications

Scratching of the skin spots should be avoided as this may cause bacterial infection and possibly leave permanent scars. Some patients, especially the elderly or those with other illnesses, may develop pneumonia. This causes breathing difficulties, cough and fever, and requires treatment in hospital with special anti-viral drugs. Very rarely inflammation of the brain may occur. This produces severe headache and sensitivity to light. The doctor must be contacted.

Shingles

After chickenpox, the virus never leaves the body completely but lies dormant in nerve fibres. It affects the nerves and other tissues of the skin. The condition usually starts with fever and burning pain in the areas connected with the affected nerve. Four to five days later a skin rash appears usually on one side of the trunk or face. The rash consists of blisters on a red area of skin usually in a stripe across one half of the body only. These fluid-filled blisters on the skin later form scabs which drop off within 2 weeks.

The disease tends to be more severe if the patient’s body defences against infection are poor, for example the elderly. Some patients may suffer from persistent pain for more than 2 months after the beginning of the disease. Their sleep may be disturbed and they may feel depressed.

Shingles near the eye needs treatment

If the shingles rash is on the forehead and down the side of the nose, the eye on that side is under threat and a doctor should be consulted for referral to an eye specialist.

The shingles rash can cause chickenpox

Shingles cannot be passed on to others as shingles, but it is possible to catch chickenpox from somebody suffering from shingles if you have not had chickenpox before. The blisters are full of chickenpox virus. Once the skin has healed, there is no further risk of spreading the infection to others.

The treatment depends on the severity of the disease. Mild attacks will be treated with painkillers like paracetamol or co-codamol. Calamine lotion put on the rash may help. In severe cases affecting the eye an antiviral drug, aciclovir, is necessary and must be started early. For the majority of patients with shingles elsewhere on the body, using antiviral treatment does not affect the outcome and is not necessary.

It quite often happens that the pain of shingles lasts for many months after the rash and blisters have completely healed, due to damage to the nerves. This can be very uncomfortable. In this case, antidepressant drugs in a low dosage may modify the pain. They work quite well for nerve pain. Do let us know if you are having difficulty with pain