.Never had a problem with fleas in my life. My question is how long do I need to wait to let my dog outside and walk on the area where I sprayed?

Thank you for your question. All of our herbicides and insecticides are safe to use in households with children and pets. You do need to keep children and pets off and out of treated area until the product has completely dried. After dry, the area is completely safe for your children and/or pets.