Some essential oils are effective parasites repellents: Peppermint, Neem, Eucalyptus, Cedarwood, Citronella and Lemon.
Recommended mixture for ticks:
10 drops Tea Tree
10 drops Lavender
10 drops Peppermint
How to use them: add 10-15 drops of essential oil to 15 ml carrier oil (organic vegetable oil). Massage the oil into the fur with your hands.
Alternatively prepare a spray consisting of 100 ml of vodka and 20 drops of essential oil. Apply on the fur.
Do not put the oil near the eyes, nose, anal or genital area.
Use only natural, 100% pure essential oils.
Use the essential oils recommended above. There are some oils may be unsafe for dogs, so do your research first before experimenting with other oils.