Biology Question #1921

Davina, a 12 year old female from Vancouver, Canada asks on February 15, 2004,

Why is it that when you get the chicken pox when you're little it's not as bad as getting it when you are older?

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The answer

Barry Shell answered on February 29, 2004

There is no easy answer. It is true that chicken pox is much milder in children than in adults. This is in part--and only in part--due to children developing inside a mother who had chicken pox earlier in life and getting immunity from the mother while in the womb. This means children under 1 year of age rarely get chicken pox. Children 2 and up start catching chicken pox as their maternal immunity wears off. Toddlers (2 - 3 years old) can get it, but often get a milder form of the disease. (DISCLAIMER: the range of severity of disease in a given child, even a toddler or baby, is significant, so just because on average they have milder disease, this means some children of this young age can get full blown chicken pox, perhaps very severe, even though they had some maternal immunity). As children age, this immunity wears off even more. In addition to this, there does appear to be some other mysterious difference between adults and children that makes chicken pox in adults much worse. Since there are many hormonal and other biochemical differences between adults and children we don't know the exact cause, but in the message is: either get chicken pox when you are young, or preferably, get immunized when you are young.

Once you get chicken pox, the virus lives in certain nerve cells in your body for the rest of your life. It's harmless, except the virus can become "re-activated" if you ever stress your body in some big way (little sleep, another sickness, emotional stress or whatever). This reactivated virus infection is a disease called shingles and causes severe pain especially of nerves around the face, eyes, and scalp. It always occurs on just one side of the body. Only people who had chicken pox can get shingles. It's a "disease-coming-from-within" rather than an infectious disease obtained from another person. Shingles can be particularly bad in the elderly and so this is another reason that vaccination is encouraged to help avoid getting chicken pox in the first place.

There is a lot we don't know about our bodies and the diseases we can get. There's plenty of room for more research on chicken pox. Perhaps you, dear reader, will be the one to figure out exactly why chicken pox in adults is so much worse than in children.

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