| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Body Fat and Lipid Metabolism In high-fat-diet obese rats, olfactory stimulation (inhalation) with fennel essential oil decreased body weight, body fat, and visceral fat, and improved lipid metabolism markers and blood pressure. A separate study in dyslipidemic rats showed fennel volatile oils improved oxidative stress and inflammatory markers with superior anti-inflammatory properties. | Improves (the measure goes down) | Small effect | 2 studies | |||
Studies that measured body fat and lipid metabolism | ||||||
Supplement
Fennel essential oil is an aromatic oil from the fennel plant, rich in compounds like anethole. The main human research looks at diarrhea-predominant irritable bowel syndrome, where one trial of 121 people found symptoms eased about twice as much with a curcumin and fennel oil blend as with placebo, though the evidence is limited. Since the oil was tested alongside curcumin, its own effect is unclear, and most other findings come from animal or lab studies.
Sources: PMID 27308645
- Updated
- How we grade
- 18 studies cited
- Best evidence
- Grade C
- Conditions studied
- 4
- Outcomes
- 10
- Graded outcomes
- 0019
Evidence by condition
- Strong
- Moderate
- Limited
- Very limited
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| IBS Symptom Severity A multicenter RCT of 121 IBS patients found that a curcumin + fennel essential oil combination significantly decreased IBS-SSS scores by ~50% after 30 days vs ~26% for placebo (P<0.001), with 25.9% becoming symptom-free vs 6.8% on placebo. However, fennel essential oil was tested in combination with curcumin, so its independent contribution cannot be isolated. | Improves (the measure goes down) | Moderate effect | 1 study | 121 people | ||
Studies that measured ibs symptom severity | ||||||
General
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Antifungal Activity Multiple in vitro studies demonstrate fennel essential oil has potent antifungal activity against dermatophytes (T. rubrum, T. tonsurans, M. gypseum) surpassing fluconazole and amphotericin B, as well as activity against Candida species and food-borne fungi. The mechanism involves cell membrane disruption and mitochondrial enzyme inhibition. No human trials have been conducted. | Improves (the measure goes up) | Moderate effect | 5 studies | |||
Studies that measured antifungal activity
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| Antimicrobial Activity Multiple in vitro studies show fennel essential oil has broad antimicrobial activity against foodborne pathogens, Gram-negative bacteria, and S. aureus strains. When combined with antibiotics like mupirocin and cefoxitin, fennel EO enhanced inhibition zones, suggesting potential for antibiotic synergy. Activity against T. vaginalis was also demonstrated in vitro. | Improves (the measure goes up) | Small effect | 4 studies | |||
Studies that measured antimicrobial activity
| ||||||
| Cancer Cell Proliferation In vitro studies show fennel essential oil induces cell cycle arrest and apoptosis in MCF-7 breast cancer cells (in combination with geranium oil) and demonstrates cytotoxicity against breast (MDA-MB), cervical (HeLa), and leukemia (CCRF-CEM) cell lines with IC50 values below 10 μg/mL in some studies, while showing selectivity for cancer over normal lymphocytes. All evidence is preclinical. | Changes; see studies | Small effect | 3 studies | |||
Studies that measured cancer cell proliferation
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| Liver Enzyme Levels In a rat model of CCl4-induced liver damage, fennel essential oil decreased serum AST, ALT, ALP, and bilirubin levels, demonstrating hepatoprotective action. A separate animal study confirmed cardio- and hepatoprotective effects of fennel volatile oils in a dyslipidemic rat model. No human data available. | Improves (the measure goes down) | Small effect | 2 studies | |||
Studies that measured liver enzyme levels | ||||||
| Intestinal Inflammation In a rat acetic acid-induced colitis model, fennel essential oil decreased MPO activity and TNF-alpha expression in colon tissue and inhibited NF-kB p65 protein expression, demonstrating anti-inflammatory effects on intestinal inflammation through NF-kB pathway inhibition. | Improves (the measure goes down) | Moderate effect | 1 study | |||
Studies that measured intestinal inflammation | ||||||
| Wound Healing In a rat wound healing model, fennel essential oil components fenchone and limonene significantly improved wound contraction and re-epithelialization by day 10, increased collagen synthesis, and decreased inflammatory cell infiltration compared to controls. | Improves (the measure goes up) | Small effect | 1 study | |||
Body Composition
- Body Fat and Lipid Metabolism: improves
Anxiety Disorders (Other)
- Anxiety Symptoms: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anxiety Symptoms In a mouse study, fennel essential oil at 100-200 mg/kg significantly increased time spent and entries into open arms of the elevated plus maze test, and reduced rearing behavior in the staircase test, suggesting anxiolytic activity comparable to diazepam. No human trials exist. | Improves (the measure goes down) | Small effect | 1 study | |||
Studies that measured anxiety symptoms | ||||||
Cardiovascular Health
- Thrombosis Risk: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Thrombosis Risk In an animal thrombosis model, fennel essential oil (30 mg/kg orally for 5 days) provided 70% protection against collagen-epinephrine-induced paralysis, and trans-anethole provided 83% protection, without the prohemorrhagic side effects seen with aspirin. Mechanisms involved antiplatelet activity, clot destabilization, and vasodilation. | Improves (the measure goes down) | Moderate effect | 1 study | |||
Studies that measured thrombosis risk | ||||||
Key findings
- IBS Symptom SeverityImproves (the measure goes down)
- Antifungal ActivityImproves (the measure goes up)
- Antimicrobial ActivityImproves (the measure goes up)
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- Grade C
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Studies cited
18 studies from PubMed
- Olfactory Stimulation by Fennel (Foeniculum vulgare Mill.) Essential Oil Improves Lipid Metabolism and Metabolic Disorders in High Fat-Induced Obese Rats
- Foeniculum Vulgare and Pelargonium Graveolens Essential Oil Mixture Triggers the Cell Cycle Arrest and Apoptosis in MCF-7 Cells
- Analysis and evaluation of the antimicrobial and anticancer activities of the essential oil isolated from Foeniculum vulgare from Hamedan, Iran
- In Vitro Activity of Foeniculum vulgare and Its Main Essential Oil Component Trans-Anethole on Trichomonas vaginalis
- Foeniculum vulgare essential oil ameliorates acetic acid-induced colitis in rats through the inhibition of NF-kB pathway
- Health Benefits of Fennel, Rosemary Volatile Oils and their Nano-Forms in Dyslipidemic Rat Model
- Essential oil extraction, chemical analysis and anti-Candida activity of Foeniculum vulgare Miller - new approaches
- Cytotoxicity of the Essential Oil of Fennel (Foeniculum vulgare) from Tajikistan
- Effects of Foeniculum vulgare essential oil compounds, fenchone and limonene, on experimental wound healing
- The effect of fennel essential oil in combination with antibiotics on Staphylococcus aureus strains isolated from carriers
- Curcumin and Fennel Essential Oil Improve Symptoms and Quality of Life in Patients with Irritable Bowel Syndrome
- In vitro antifungal activity and mechanism of essential oil from fennel (Foeniculum vulgare L.) on dermatophyte species
- Evaluation of anxiolytic activity of the essential oil of the aerial part of Foeniculum vulgare Miller in mice
- Antimicrobial activities of essential oil and hexane extract of Florence fennel [Foeniculum vulgare var. azoricum (Mill.) Thell.] against foodborne microorganisms
- Protective effect of Foeniculum vulgare essential oil and anethole in an experimental model of thrombosis
- Comparative essential oil composition and antifungal effect of bitter fennel (Foeniculum vulgare ssp. piperitum) fruit oils obtained during different vegetation
- Hepatoprotective effect of Foeniculum vulgare essential oil
- Essential oil composition and antifungal activity of Foeniculum vulgare Mill obtained by different distillation conditions