When to stop wearing socks for baby ?

My baby's ifc teachers and the TCM physician told me to keep baby's shoulders covered, tummy (belly button) covered and sole of feet covered so that they won't always fall sick. I stopped wearing bootees for her since she reached 4 or 5mo. but she has been falling sick. so now I always let her wear socks or pants w bootees. (but that is just for our case bec i send her to an ifc that has to be aircon all the time due to its location/situated right next to a foodcourt). Not really answering ur question, but hope to help in terms of advice from TCM physician to keep impt points well covered! cheers!