How long before my 2yr old shows symptoms of chicken pox, after being exposed?

7-14 days. Your child should have been vaccinated at 1 year but if he wasn't it takes 7-14 days to incubate before you will see symptoms.
10-21 days fm expose. If you have an unvaccinated child with a known exposure time, the proper quarintine would start at 10 and go to 21 days.If your child was properly vaccinated i would skip the drauma of quarintine and simply be aware that a few vaccinated kids remain susceptable but rarely have a full case.Pregnant susceptable women & susceptable adults have the more intense problems with this disease.