Ticks...bloodsucking, disease-spreading parasites. Unless you are looking for Lyme disease, there is no positive to having a tick on your pooch!
Here is a simple homemade repellent to use on your dog.
Repellent for Pets: Add 1 cup of water to a spray bottle, followed by 2 cups of distilled white vinegar. Ticks hate the smell and taste of vinegar, and will be repelled by this ingredient alone. Then, add two spoonfuls of vegetable or almond oil, which both contain sulfur (another natural tick repellent).
To make a repellent that will also deter fleas, mix in a few spoonfuls of lemon juice, citrus oil, or peppermint oil, which will all repel ticks and fleas while also creating a scented repellent. Spray onto the pet's dry coat, don't get it in their eyes (or other sensitive areas). Spray down your pet once per day if they are only going outside to go to the bathroom, spray them several times a day if they spend the entire day outside.
Remember even if using a tick repellent to give your dog a good check over especially when playing in long grass!