Here is an article from Scientific American on how effective catnip is in repelling mosquitoes.

Felines' Favorite Herb Proves Abhorrent to Mosquitoes
Your feline may find it irresistible, but catnip has rather a different effect on mosquitoes. Indeed, according to findings presented yesterday at a meeting of the American Chemical Society, nepetalactone, the essential oil that lends the plant its characteristic scent, repels the pesky insects about 10 times more effectively than does DEET, the active ingredient in most commercial insect repellents.
Earlier work carried out by Joel Coats of Iowa State University and then–postdoctoral researcher Chris Peterson had revealed the cockroach's dislike of catnip. The same team thus decided to investigate whether mosquitoes might share that opinion. Placing groups of 20 mosquitoes in a glass tube, half of which was treated with a high dose (1 percent) of nepetalactone, the researchers found that after 10 minutes, only 20 percent of the insects remained on the treated side. When they tested the effects of a lose dose (0.1 percent) of the catnip oil, 25 percent of the mosquitoes stayed in the treated area. In contrast, when the team ran the same experiment with DEET (diethyltoluamide), 40 to 45 percent of the bugs held their ground on the treated side of the tube.
Peterson notes that it takes about one tenth as much catnip oil as DEET to have the same repellent effect on the mosquitoes. Though the team only used the so-called yellow fever mosquito, Aedes aegypti, in their experiments, they say nepetalactone should prove similarly abhorrent to all mosquito species. What the researchers can't explain is why the catnip drives the insects away in the first place. "It might simply be acting as an irritant or they don’t like the smell," Peterson offers. "But nobody really knows why insect repellents work."
If it proves safe for people, nepetalactone could one day find its way into commercial products. In the meantime, the Iowa State University Research Foundation has submitted a patent application for use of the catnip compounds as insect repellents.                  —Kate Wong CHEMISTRY- Scientific American Aug 2001

What are Essential Oils?

Essential oils are the subtle, aromatic and volatile liquids extracted from the flowers, seeds, leaves, stems, bark and roots of herbs, bushes, shrubs and trees, through distillation. According to ancient Egyptian hieroglyphics and Chinese manuscripts, priests and physicians were using essential oils thousands of years before Christ to heal the sick. They are the oldest form of
medicine and cosmetic known to man and were considered more valuable than gold. There are
188 references to oils in the Bible. The wise men brought the Christ Child gold, frankincense
and myrrh. (Clinical research now shows that frankincense oil contains very high immune
stimulating properties.) In Exodus God gives Moses the formula for "an holy anointing oil".
(Exodus 30:22-25) Some of the precious oils which have been used since antiquity for anointing
and healing the sick are frankincense, myrrh, galbanum, hyssop, cassia, cinnamon, and
spikenard. Science is only now beginning to investigate the incredible healing substances found in essential oils.
Essential Oils have a  penetrating characteristic that  greatly enhances their ability to be effective. Essential oils will  quickly penetrate into the body when applied to the skin. Essential oil placed on the foot will be distributed to every cell in the body in 21 minutes. They will even
penetrate a finger or toe nail to treat fungus underneath.
Essential Oils  are highly aromatic and therefore, many of the benefits can be obtained by
simply inhaling them.
Essential oils, when diffused, have been known to be the best air filtration system in the world.
Benefits:Purify, by removing metallic particles and toxins from the air.
Increase atmospheric oxygen.
Increase ozone and negative ions in the house, which inhibits bacteria growth.
Destroy odors from mold, cigarettes, and animals.
Fill the air with a fresh, herbal aromatic scent.
Pure Essential Oils Have Very High Frequency
The effectiveness of essential oils cannot be fully understood without some discussion of
frequency. Frequency is the measurable rate of electrical energy flow that is constant between any two points. Everything has frequency. Dr. Robert O. Becker in his book "The Body Electric" established that the human body has an electrical frequency and that much about a person's
health can be determined by it's frequency.
In 1992, Bruce Tainio of Tainio Technology, an independent division of Eastern State University in Cheny, Washington, built the first frequency monitor in the world. Tainio has determined that the average frequency of the human body during the day time is 62 - 68 Hz. (A healthy body frequency is 62 - 72 Hz.) When the frequency drops, the immune system is compromised. If the frequency drops to 58 Hz, cold and flu symptoms appear, at 55 Hz, diseases like Candida take
hold, at 52 Hz, Epstein Bar and at 42 Hz, Cancer.
Every living thing has a frequency, including diseases-According to Dr. Royal R. Rife, every
disease has a frequency. He found that certain frequencies can prevent the development of
disease and that others would destroy disease. Substances with higher frequency will destroy
diseases of a lower frequency. The study of frequencies raises important questions, concerning
the frequencies of substances we eat, breath and absorb. Many pollutants lower healthy
frequency. Processed/canned food has a frequency of zero. Fresh produce has up to 15 Hz, dry
herbs from 12 to 22 Hz and fresh herbs from 20 to 27 Hz. Essential oils start at 52 Hz and go as
high as 320 Hz, which is the frequency of rose oil.
Clinical research shows that essential oils have the highest frequency of any natural substance known to man, creating an environment in which disease, bacteria, virus, fungus, etc., cannot live.