Here is a recipe to discourage pests from biting and annoying you while outside.
Herbal Pest Discourager
15 drops lemon eucalyptus essential oil
10 drops pennyroyal (or peppermint, but pennyroyal works best) essential oil
10 drops white thyme essential oil
10 drops lavender 40/42 essential oil
5 drops basil essential oil
3 drops tea tree essential oil
Combine essential oils in a glass or PET bottle with 3 oz. of jojoba oil, cap and shake or mix with 3 oz. distilled water and 1 TBLS of polysorbate 20.
Dispense water-based solution with fine mist sprayer.
I think this is from The Herb Companion. You can get these ingredients from a health food store.