Citiraj:
The most common (and most effective) natural insect repellents are various essential oils. Clove oil and citronella (rose geranium) are the most effective against mosquitoes, but be careful with clove oil and use it sparingly. It can be a skin irritant. Other fairly effective essential oils include lemon grass, eucalyptus, castor oil, peppermint, tea tree oil, lavender, and cedar. You can buy cedar oil in spray-on bottles at your local pet store.
It's important to remember when using essential oils that you shouldn't use them internally! They need to be used externally on your skin and garments. Be sure to test any oils on a small patch of skin before applying widely to your body to avoid allergic reactions or skin irritations.
You can make your own insect repellent sprays by combining rubbing alcohol (or witch hazel, vodka, or olive oil) with one of the listed essential oils (about 10-to-1, alcohol-to-oil ratio). Shake well before each use.
To make a lotion, use two ounces of distilled water, two ounces of olive oil, and about 120 drops essential oil. Put the water into a deep mixing bowl, and using a wire whip, begin beating quickly while slowly drizzling in the olive oil. After oil is mixed into the distilled water, stir in the essential oil of your choice (citronella is probably the most effective for insect repellent use).
You can also add a few drops of your choice of insect-repelling essential oils to your shampoo or liquid soap to help counteract the perfumes in these products.
Keep in mind that clothing rubbing on your skin, natural evaporation, your skin's natural ability to absorb anything applied to it, sweat or rain washing off the repellent, and a windy environment reduces the effectiveness of all insect repellents.
Some folks claim that garlic is an effective insect repellent, but I think it works best for repelling friends (and maybe a vampire or two).