Couple things to consider...
Washing: Hand wash with cold- luke warm water with any detergent. Air dry, tumble dry with no heat, or press against the skin for 9 hours under a down garment.
A lesson on Stabilizer: Stabilizer is a cloth, paper, or water soluble plastic that is placed on the backside of an embroidery to give it structure. I mainly use paper so that the handkerchief softens with use and wash. This may eventually lead to some puckering but the function of a handkerchief is to be soft.
IF YOU HAVE AN EMBROIDERY THAT HAS A VISIBLE BACKSIDE (I.E. LOGOS):
There will be visible stabilizer on the reverse side of the handkerchief (the customer has discretion on removal). This is water soluble and can be easily removed by submerging the handkerchief in water and gently agitating or by poking at it with a wet sponge. It will either be a tough white cloth or a clear plastic.