Corn Gluten is certainly safe for the dog.  However, corn gluten is a weed preventer not a weed killer.  It will prevent seeds from germinating.  Weed seeds, crabgrass seeds…all seeds including good grass seeds will be prevented from germinating.  It WILL NOT kill existing perennial weeds, like dandelions that are growing from an already established root system.  For those, you’ll need to use an actual weed killer.  Liquid sprays are the most effective.  We sell Weed Beater Ultra.  This is a spray that you’ll spray on the leaves of the weeds.  It is absorbed through the leaves of the weeds only.  It kills the roots but has to enter through the leaves.  It is still too early to use weed killer sprays (4/30/14)…it is a little too cool still.  Night time temperatures want to be 45° or above for the weed killer spray to work.  Since it is absorbed through the leaves, it needs to remains in contact with the leaves for at least 24 hours.  Don’t water after application and don’t apply when rain is expected within 24 hours.  These liquids are safe for pets as you don’t let the dog walk on the lawn while the spray is wet.  I’d keep the dog off the treated area until rain has washed the weed killer into the soil.  The nice thing about the liquid spray is that you can treat the lawn in sections and don’t bother spraying areas where there are no weeds.  As always, always read the label before using and follow the instructions to the letter.