Will concealer left overnight ruin the growth of my new hair?

You are not going to harm your grafts 2 months after a hair transplant but in the next few months the new hairs are coming in so you want to minimize any irritation or inflammation. I would recommend washing toppik off every night to prevent unnecessary build-up of the product and prevent inflammation.  If this is not possible, just be on the lookout for pimples or pustules as the new hairs grow in.  Contact your surgeon if this occurs and increase the frequency that you shampoo.

Thank you for posting your question. Being 2 months post procedure, you should be perfectly safe. Do your best in making sure you are using an organic based product. Also make sure the skin pores are cleaned out very nicely, so once the grafts that start growing 3 to 4 months out, they don't become ingrown. Hope this helps.