My 7 year old son falls sick easily upon attending K1 onwards, what could be the reasons?

If this is the 1st time your child is going to childcare or kindergarten, it could most likely because of the viruses that it running around. Your child may not have the immunity to conquer the viruses yet which is actually quite common. They will normally get used to it in 3-6 mths time depending on the child as well. You may wish to boost his immunity level so that he can fight all these better. You may wish to give him extra Vitamin C or Multivitamins. Don't forget that all supplements take time to work as well.