I like Neem oil (from Neem tree in India, I believe) for an insect repellent. There are a few manufacturers of Neem products for people and pets. It works great for ticks but is used for fleas, as well. According to the web site info, it is also safe for use with puppies and kittens. Usually, there are other essential oils inlcuded in the ingredient list along with the Neem.
Here are a couple of links to check out. They can be ordered online but they should also be available at your local health food store.
Neem Product Link