What is Dog Fennel?
Dog fennel (Eupatorium capillifolium) is also known by other common names such as false fennel, Carolina fennel, and Prairie dock. It is a perennial herbaceous plant that grows 3-5 feet tall with small yellow flower heads arranged in large, flat-topped clusters. The leaves are almost hairless and very finely divided, giving the plant a feathery or lacy appearance which is why it is sometimes called dog fennel.
Dog fennel is native to North America and grows throughout most of the central and eastern United States, from Texas to Massachusetts and south to Florida. It thrives in open fields, pastures, roadsides, and disturbed areas with full sun exposure. Dog fennel spreads aggressively by rhizomes and prolific seed production.
Mosquito Repellent Claims
There is a common belief that dog fennel can help repel mosquitoes. This idea likely stems from the strong odor released by the crushed leaves of the dog fennel plant. The potent smell is similar to camphor or eucalyptus, and some believe it can overpower human scents that attract mosquitoes.
Additionally, some think that burning or rubbing the leaves releases natural oils that repel mosquitoes. There are many home remedy sites and blogs that recommend using dog fennel in various ways, such as making torches from the stalks or rubbing the leaves on your skin.
The smell of dog fennel can be quite pungent, so it’s understandable why some feel it has mosquito repelling properties. However, there is little scientific evidence to back up these claims.
Evaluating the Claims
There has been some scientific research into the mosquito repelling properties of dog fennel, but the evidence is still limited. Some initial studies have shown that extracts and essential oils from the dog fennel plant do have insecticidal effects against mosquitoes.
One study found that an ethanol extract of dog fennel was toxic to mosquito larvae and could potentially be used as a natural insecticide. The researchers identified several active compounds in the extract like limonene, carvone and piperitone that likely contribute to its mosquito-repelling abilities.
Another study tested the essential oils from dog fennel against the Southern House Mosquito. They found the essential oil to have larvicidal activity and was able to kill a significant portion of mosquito larvae. The researchers noted that the toxicity was likely due to active chemicals like trans-carveol and cis-carveol.
While these initial studies show promise for dog fennel’s mosquito repelling properties, more research is still needed to conclusively determine its effectiveness specifically as a natural repellent for humans. The active chemicals would need to be thoroughly evaluated for safe topical application at an effective concentration.
Other Mosquito Repelling Plants
In addition to dog fennel, there are several other plants that have natural mosquito repelling properties, including:
Citronella
Citronella is likely the most well-known natural mosquito repellent. The citronella plant contains citronella oil, which has been registered as an insect repellent by the Environmental Protection Agency (EPA) since 1948. Citronella oil is a common ingredient in many commercial insect repellents. Research shows that citronella oil repels mosquitoes effectively, but it needs to be reapplied frequently.
Catnip
Catnip contains a chemical called nepetalactone, which is known to repel mosquitoes. Crushing and rubbing fresh catnip leaves on your skin can provide some short-term mosquito repellency. Some studies show catnip oil to be as effective as DEET at repelling mosquitoes.
Lemon Balm
Lemon balm contains citronellal, which gives the leaves a lemon-like scent that helps repel mosquitoes. Crushing the leaves and applying to the skin can provide temporary protection. Oils from lemon balm have also been shown to be effective at repelling mosquitoes in laboratory studies.
Basil
Fresh basil contains oils like citronellol, linalool, and geraniol that have mosquito repelling properties. Rubbing crushed basil leaves on exposed skin can provide short-term protection against mosquito bites.
Marigolds
Certain varieties of marigolds contain pyrethrum, a compound used in many mosquito sprays and foggers. Interplanting marigolds near areas where you gather outdoors can help deter mosquitoes.
While plants like citronella, catnip, and lemon balm can repel mosquitoes similar to dog fennel, they need to be reapplied frequently for ongoing protection. None of these plants provide complete protection on their own like a DEET-based mosquito spray.
Risks of Dog Fennel
Although some claim dog fennel repels mosquitoes, this plant does come with some risks that should not be overlooked.
One potential issue with dog fennel is that it can cause skin irritation in some people. The plant contains chemicals that can cause dermatitis when handled. Direct contact with dog fennel may lead to redness, itching, and inflammation for sensitive individuals.
Dog fennel can also be toxic to livestock such as cattle and horses. All parts of the plant are poisonous if ingested by these animals. Symptoms of poisoning include vomiting, diarrhea, weakness, and breathing issues. In severe cases, toxicity can be fatal. Livestock owners should take care to remove dog fennel from fields and pastures.
Additionally, dog fennel spreads aggressively and is considered an invasive weed in many areas. It spreads rapidly via wind-dispersed seeds and can quickly take over open spaces. Allowing dog fennel to grow uncontrolled can lead to it crowding out desirable native plants and damaging ecosystems.
Safe Uses
Dog fennel can be safely used as a mosquito repellent when handled properly and applied correctly.
Proper Handling Precautions
When harvesting or handling dog fennel:
- Wear gloves, long sleeves and pants to prevent skin irritation
- Wash hands after contact with the plant
- Avoid touching your eyes or face during handling
- Keep away from open wounds
- Do not ingest dog fennel
Recommended Applications
To use dog fennel for mosquito repelling:
- Hang bunches of dried dog fennel near outdoor gathering areas
- Rub crushed leaves directly on exposed skin
- Burn dried dog fennel leaves or use in citronella candles outdoors
- Add leaves to bath water
Dosage and Preparation
When applying topically:
- Use freshly crushed leaves for maximum potency
- Test on a small area of skin first to check for irritation
- Avoid applying near eyes, nose or lips
- Reapply every 2-4 hours for continued effectiveness
Recommendations
When reviewing the evidence, dog fennel does not seem to be a very effective mosquito repellent. While there are some anecdotal reports of it working, there is no scientific research confirming its efficacy. There are several disadvantages to relying solely on dog fennel, including:
- Lack of proven effectiveness
- Allergic reactions in some individuals
- Unpleasant strong odor
- Environmental concerns in areas where it is an invasive species
Fortunately, there are several alternatives with much more evidence supporting their use as mosquito repellents:
- DEET – The most widely used and studied synthetic mosquito repellent
- Oil of lemon eucalyptus – A plant-based oil that offers protection similar to low concentrations of DEET
- Picaridin – A synthetic repellent with effectiveness comparable to DEET
- IR3535 – A synthetic repellent derived from amino acids
- Citronella oil – A plant-based oil with some repellent effects but requires frequent reapplication
Rather than relying solely on unproven home remedies, it is recommended to use EPA-registered insect repellents for the best protection against mosquitoes. Dog fennel does not have enough evidence of effectiveness to be recommended as a repellent.
The Bottom Line
After reviewing the available evidence, it’s clear there is insufficient research to definitively conclude that dog fennel reliably repels mosquitoes. While some anecdotal reports suggest it may provide mild and temporary relief, there are no rigorous scientific studies proving strong mosquito repellent effects. The active chemical components that could theoretically deter mosquitoes have not been identified or isolated in dog fennel at concentrations known to effectively repel biting insects. Until more research is conducted, claims of dog fennel’s mosquito repelling powers remain unverified.
That said, there are some key points to remember:
- Traditional mosquito repellent plants like citronella, lemongrass, and catnip have much stronger evidence behind them.
- Dog fennel pollen can trigger allergies and asthma symptoms in sensitive individuals.
- Ingesting or touching dog fennel plants can cause mild skin irritation in some people.
- Dog fennel grows aggressively and is considered a weed in many areas.
While not definitively dangerous, the benefits of dog fennel for repelling mosquitoes are still in question. Standard EPA-registered insect repellents or plants with proven effects like citronella are likely safer, more effective alternatives for preventing mosquito bites.
FAQs
Is dog fennel safe to grow in my yard?
Dog fennel is considered an invasive weed in many areas, so check your local restrictions before planting it. It spreads aggressively, so containment measures may be needed.
Can I get a rash from dog fennel?
The sap of dog fennel can cause skin irritation in some people. Wear gloves when handling the plant as a precaution.
How do I use dog fennel to repel mosquitoes?
Crush the leaves to release the scent, then rub the leaves directly on your skin. Do not ingest dog fennel. Monitor for any skin reaction when first using it.
Should I plant dog fennel near my home?
Plant dog fennel far from walkways, driveways, or foundations, as it can spread quickly. Keep it contained within garden beds or borders.
Is dog fennel toxic to pets?
Ingesting dog fennel may cause gastrointestinal upset in dogs and cats. Contact your vet if your pet consumes any part of this plant.
References
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