Why is post op spraying with normal saline necessary after having Hair Transplant?

It is best to ask your surgeon about post operative care as each doctor has their unique regimen.  Saline spray is not necessary but some doctors may recommend it.

The use of post op saline helps the recipient sites to heal quicker and expedite the removal of crusts/scabs.Your grafts will get nutrients and moisture from the scalp and will not dry out.I expect you will have perfectly normal growth!

Missing one day likely did not do any significant damage to your grafts. If you are really concerned you should follow up with your doctor about it.

An FUE is treated just like a regular hair transplant with regard to the recipient area, but the donor area has open wounds which require daily washing with soap  and water. Within 3 days of surgery, you can resume full activities, heavy exercises if you wish. The recipient area requires daily washes as well to keep the recipi ent area free of crusts. I generally recommend and if you washed it properly, there will be no crusts on it, even the very next day. Use of a sponge which we supply our patients, a surgical sponge to fill with soapy water and press on the recipient area daily. By repeating this daily, all crusts can be washed off without any fear of losing grafts. IF any crusts are present, use a Q tip and dip it into soapy water, and roll it on the crusts and that will lift them off without dislodging them, but never rub them, just roll the Q tip on the recipient crust. I like to see no evidence of any crusting in the recipient area and the crusts from the donor area gone in 7-10 days with daily washing.