Can you spray off on dogs?

Most likely it contains a certain amount of DEET, which could be harmful to your pet. (I'm not too sure it's really all that good for humans.)

Your best defense would be to have your canine friend tested for heartworms and if clear, put on a monthly treatment like HeartGard.

Then use a flea and tick treatment (many are monthly) to protect your dog against other insects that can cause problems.

That's usually enough to get 'em through the year without too many problems.

If you dog has been sprayed with DEET, then probably a bath should be considered.

Since I'm not a vet, I'd really suggest that you call a local veterinarian and just ask. They should be able to tell you what's safe and what isn't. It only takes a few minutes to be sure and it could save your dog's life.