Essential oils are complex compounds, which makes them very effective in combating anything that is also natural in nature, such as mosquitoes, ticks, fleas and worms. Unlike synthetic medicine, essential oils work with the body rather than against it. Because of this, essential oils can be more effective at fighting naturally occurring pests. One thing to take take note is that high quality oils sometimes are not typically found in drugstores, grocery stores, or most health food stores. Essential oils can be obtain from small company or individual that sells only aromatheraphy grade, therapeutic oils. Many sources will say their oils are pure, but that may not always be the case.

Essential oils are derived from plants, frequently herbs. However they are different from herbal remedies in that the oils are extracted from various parts of the plant, whereas herbal remedies are made from the entire plant.
Mosquitoes, ticks, and fleas are repelled by a variety of essential oils but lavender, lemongrass and peppermint are especially effective against most pests that effect your dog's health. The essential oils will be absorbed into your dog's body through his coat and skin, also providing internal protection.

Essential oils are also very good at removing internal parasites such as tapeworm or roundworm. Be very careful when administrating essential oils internally. Do your research first and err on the side of caution. Diffusing the oils in nebulizer or diluting them can also help to remove internal parasites. Do not use essential oils internally if you are in doubt. Seek the advice of a holistic veterinarian who is familiar with using essential oils before embarking upon this type of treatment.