Grapefruit Seed Extract: Benefits, Dosage, Safety & Purity

Grapefruit seed extract, often shortened to GSE, is a bitter concentrate made from the seeds of grapefruit, and people use it as a natural antimicrobial against yeast, bacteria and household mold.9410

Grapefruit seeds usually end up on the side of the plate. Ground and extracted, those seeds and the pulp around them carry bitter compounds called limonoids along with citrus flavonoids, the same families of compounds that give the fruit its sharp taste.911 As remedies go, it's a young one, developed in 1980.1

Grapefruit seed extract is one of the eight antifungals in my Candida Cleanse Protocol, at 250 mg or 10 drops twice a day.4 It's a strong one, so start low and pair it with probiotics.4

Did you know?

• The food industry uses grapefruit seed extract as a natural preservative.12

• Japan lists grapefruit seed extract as a natural food additive.7

• Beekeepers have used grapefruit seed extract as an organic treatment for American foulbrood, a bacterial disease of honeybees.13

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What is grapefruit seed extract?

The seeds are rich in limonoids, the bitter compounds behind their taste. Limonin is the main one, followed by nomilin, and researchers have isolated obacunone, deacetylnomilin and a limonin glucoside from red grapefruit seeds as well.916 An extract of the seeds and pulp also carries polyphenols, including the flavonoids naringin and hesperidin.11

Those compounds act as antioxidants in the lab. An acetone extract of red grapefruit seeds neutralized 85.7% of a test free radical at 500 parts per million, and a glycerin extract of the seeds showed antioxidant activity in three different lab tests.1617 Which compounds drive the extract's action against microbes is still an open question: in a 2021 lab study, naringin, its main flavonoid, didn't account for its activity against staph.2

Product labels don't always tell you which parts of the fruit went in. When researchers at the University of Mississippi analyzed 17 commercial products, many contained a wide range of flavonoids, a sign that peel, pulp or seed coat were used along with the seeds.9 That matters for medication safety, covered in the safety section.

A short history of grapefruit seed extract

Jacob Harich, an American immunologist, is credited with developing grapefruit seed extract.1 In the decades since, it has found its way into supplements, cosmetic ingredients and household sprays, and into products for organic farming.718 As its use spread, government and university labs began testing what was inside the bottles, the story told in the next section.

How do you choose a pure grapefruit seed extract?

The labs used chemical fingerprinting methods, such as liquid chromatography and NMR, to identify what each product contained. Here's what six analyses with product counts found, 85 products in all:

Other labs found the same chemicals. In 1996, Japan's national health-sciences institute found that two of the three main peaks in a commercial food-additive extract were methylparaben and triclosan, a profile quite different from an extract the researchers made from grapefruit seeds themselves.19 In 2001, USDA chemists identified benzethonium chloride as the main compound in what they extracted from commercial liquid and powder products, at 8.03% of the liquid and higher in the powders, and in 2005 they found benzalkonium chloride in others.2021 A Swedish method study measured about 78 mg of benzethonium chloride per milliliter in one product.22 Italian researchers found related disinfectants in extracts used by beekeepers, with each sample's antimicrobial effect closely tracking the additives it held.13 And in 2020, Johns Hopkins researchers who screened two commercial extracts before a Lyme disease study found elevated levels of benzalkonium chloride in one of them and used only the clean one.8

These are synthetic disinfectants. Benzethonium and benzalkonium chloride are used in cosmetics and cleaning products, and in 2016 the FDA ruled that triclosan and 18 other ingredients were not generally recognized as safe and effective in consumer antiseptic washes, while deferring its decision on benzethonium and benzalkonium chloride.202123 I've long told people to keep antibacterial chemicals like triclosan out of their homes, because they kill off good bacteria.2425 A product sold as a natural extract shouldn't be carrying them.

What does the extract do without the disinfectants?

Two products with the disinfectants ruled out or accounted for still showed strong activity in the lab. One whose maker confirmed it held no benzethonium chloride stopped drug-resistant staph. Another held a little benzalkonium chloride, but the researchers showed that amount on its own couldn't do what the extract did: inactivate Salmonella and E. coli within seconds. Both studies are in the ranked benefits below.226

Results vary by product and test. In the 1999 German study, the one product with no preservative showed no antimicrobial activity, and neither did extracts the researchers made themselves from grapefruit seed and pulp, so the authors credited the other five products' activity to their preservatives.6 An extract of grapefruit seed and pulp made in a Croatian lab stopped 20 kinds of bacteria and 10 yeasts at concentrations of 2.06% to 16.50%.11

How to buy a clean grapefruit seed extract

Look for these before you buy:

• A lab report, or certificate of analysis, showing the product was tested for benzethonium chloride, benzalkonium chloride and triclosan, the disinfectants these analyses found147

• No synthetic preservatives on the label, such as benzethonium chloride, benzalkonium chloride, triclosan or parabens18

• The source stated plainly: grapefruit seed, and whether pulp or peel went in too9

• A maker that answers your questions about testing; a short ingredient list on its own isn't proof of what's in the bottle15

What is grapefruit seed extract good for?

Grapefruit seed extract benefits: what the research shows

Ranked by how directly the research tested grapefruit seed extract in people, its benefits start with less Candida yeast in the gut, then calmer digestion and clearer nasal passages, with strong lab support against drug-resistant bacteria and as a surface disinfectant.

Grapefruit seed extract for Candida: does it work?

Candida albicans is a yeast that lives in most people's gut, held in check by a healthy microbiome. Sugar, alcohol, refined flour, a stretch of high stress and courses of antibiotics can tip that balance, and an overgrowth can follow.4 Clearing it takes more than one herb, which is why grapefruit seed extract has a set place in a larger plan.

Where grapefruit seed extract fits in a candida cleanse

My Candida Cleanse Protocol runs 30 to 35 days in four phases, and the order matters: starve the yeast, open your drainage pathways, kill, then rebuild.4 Grapefruit seed extract belongs to the kill phase, days 14 to 28. Here's how the protocol uses its antifungals:4

1. Starve and open first. Start the candida diet on day 1 and get your bowels, liver and kidneys moving before the kill phase, so what dying yeast releases can leave your body.
2. Break the biofilm. Take NAC and serrapeptase on an empty stomach 30 to 60 minutes before your antifungals.
3. Combine and rotate. The protocol ranks eight antifungals, including caprylic acid, oregano oil, berberine, pau d'arco, garlic, olive leaf extract and grapefruit seed extract. Combine two or three and rotate every 7 days so the yeast can't adapt.
4. Take it with food, twice a day, for the full 14 days, and start at half the dose for 3 days if you're sensitive.
5. Pair it with probiotics, then rebuild your gut once the kill phase ends.

Mild die-off is common in a kill phase, and the safety section below covers what's normal and what isn't.

What the studies show in people

The first human study of grapefruit seed extract came from a German clinic in 1990. Twenty-five people aged 16 to 41 with severe eczema, 14 of whom also had gut symptoms, took a commercial citrus seed extract for 4 weeks, with no comparison group. The 10 who took the liquid, 2 drops in 200 mL (about 7 ounces) of water twice a day, saw no significant change in their stool bacteria, and 2 of them reported better digestion.

The 15 who took capsules, three 50 mg capsules three times a day for 450 mg in all, saw Candida and Geotrichum yeasts in their stool fall from 40,000 to 250 colony-forming units per gram, a count of live yeast, and hemolytic coliform bacteria and staph fell too.3 All 15 reported less constipation, gas and abdominal discomfort and better sleep, and no side effects were recorded.3 One author worked for a U.S. supplement company, and the extract itself wasn't analyzed.3

A larger study came from Germany in 2024. One hundred adults, 85 of them women, with chronic indigestion or irritable bowel symptoms took a glycerin extract of grapefruit seeds and peel, supplied by the study's sponsor, for 8 weeks, at a suggested 15 drops three times a day, and reported their symptoms online, with no comparison group. Compared with day 1, their total gut symptom scores were 26.4% lower by day 14, 53.1% lower by day 28, 58.7% lower by day 42 and 49.9% lower by day 56. Upper-gut symptoms such as heartburn improved more than lower-gut ones, 57.9% against 47.3% at day 56.5 By the end, 72 of the 100 rated their gut complaints improved, 30 of them strongly, 1 felt worse, and the extract was well tolerated.5

How it acts on yeast

In lab tests, a commercial 33% grapefruit extract showed potent activity against 205 Candida strains taken from patients, with low activity against the fungi behind athlete's foot and against molds.1 On denture acrylic, a 1% solution of a commercial extract almost completely cleared Candida biofilm in 5 minutes, and a 0.1% solution kept inhibiting it for 24 hours. A standard denture-cleansing tablet mainly killed the round yeast cells, while the grapefruit seed extract solutions killed the thread-like hyphae Candida uses to dig into tissue as well.27 In baker's yeast, the extract triggered programmed cell death through the cell's mitochondria.33

Grapefruit seed extract dosage: how to take it

These are the amounts with a source behind them:

Around the home, I recommend it as a simple spray to help cleanse mold from the air.10

I also like grapefruit seed extract internally to help cleanse mold from the body.10 No study has yet tested it for mold illness. Our guide to detoxing your body from mold lays out the rest of that plan. For other natural options around the house and on skin, see this antifungal spray recipe and our guide to tea tree oil.

Grapefruit seed extract side effects, interactions and who should skip it

Strength is the main thing to respect. In lab tests, a commercial extract was toxic to human skin cells at every strength from full strength down to a 1-to-128 dilution, and it was harmless to them at 1 to 512, where it still killed bacteria.32 That's why the drops go into a full glass of water and never straight onto skin or into your mouth.

In the one study that counted stool bacteria in people, the helpful lactobacilli dipped slightly on capsules and the authors saw no effect on bifidobacteria, while yeast fell sharply.3 My protocol pairs the extract with probiotics, since it's a strong antimicrobial.4

Mild die-off is normal on days 2 to 5 of a kill phase: headache, fatigue, achiness or irritability. Keep going, and drop to half the antifungal dose if you need to.4

Does grapefruit seed extract interact with medications like grapefruit juice?

It may, so treat it like grapefruit. More than 85 drugs are known or predicted to interact with grapefruit, and 43 of those interactions can cause serious side effects. The cause is a group of compounds called furanocoumarins, which switch off CYP3A4, an enzyme in the gut wall that breaks down many medications, and one whole grapefruit or 200 mL of juice is enough to do it.35 In a study where 18 healthy adults each tried all three juices, a 240 mL (8-ounce) glass of regular grapefruit juice raised blood levels of the blood pressure drug felodipine about twice as high as orange juice or the same grapefruit juice stripped of its furanocoumarins. Furanocoumarins, not grapefruit's flavonoids, drive the effect.36

Citrus fruits, grapefruit's family included, keep more of these compounds in the peel than in the pulp,37 and no published study has yet measured them in grapefruit seed extract. Many products include peel or pulp, though, as noted above.9

The one reported interaction with grapefruit seed extract itself involved warfarin, and the researchers pointed to a disinfectant in the product as the cause:

That's a single case, and the likely cause was a contaminant. My protocol's rule covers it and grapefruit's own risk at once: if you take medications metabolized by the liver, clear grapefruit seed extract with your prescriber first.4 If you take a medicine on this list, here's what to do:

Never stop or change a prescription on your own; any change goes through the doctor who prescribed it. For foods and herbs that affect clotting, see natural blood thinners.

The bottom line

Grapefruit seed extract: frequently asked questions

References

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2. Han HW, Kwak JH, Jang TS, et al. Grapefruit Seed Extract as a Natural Derived Antibacterial Substance against Multidrug-Resistant Bacteria. Antibiotics (Basel). 2021;10(1):85. doi:10.3390/antibiotics10010085 · PMID:33477436
3. Ionescu G, Kiehl R, Wichmann-Kunz F, et al. Oral Citrus Seed Extract in Atopic Eczema: In Vitro and In Vivo Studies on Intestinal Microflora. J Orthomol Med. 1990;5(3):155-157.
4. Axe J. The Candida Cleanse Protocol: The 30-Day Healing Protocol. DrAxe.com. 2026 (four-phase roadmap; Phase 3 Kill, days 14-28: biofilm breaker first, rotate two or three antifungals every 7 days, with food twice daily for 14 days, half dose for 3 days if sensitive; p. 20 "Top 8 antifungals": grapefruit seed extract 250 mg or 10 drops twice daily, "Strong — start low and pair with probiotics. If you take medications metabolized by the liver, clear it with your prescriber first."; p. 26 FAQ and die-off guide: pregnancy and breastfeeding, kids, fluconazole or an antibiotic, signs that are not die-off).
5. Uehleke B, Storr M, Hörning M. Grapefruit Seed Extract Reduces Gastrointestinal Symptoms. Z Phytother. 2024;45(2):54-60. doi:10.1055/a-2194-2206
6. von Woedtke T, Schlüter B, Pflegel P, et al. Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained. Pharmazie. 1999;54(6):452-6. · PMID:10399191
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8. Feng J, Leone J, Schweig S, et al. Evaluation of Natural and Botanical Medicines for Activity Against Growing and Non-growing Forms of B. burgdorferi. Front Med (Lausanne). 2020;7:6. doi:10.3389/fmed.2020.00006 · PMID:32154254
9. Avula B, Sagi S, Wang YH, et al. Liquid Chromatography-Electrospray Ionization Mass Spectrometry Analysis of Limonoids and Flavonoids in Seeds of Grapefruits, Other Citrus Species, and Dietary Supplements. Planta Med. 2016;82(11-12):1058-69. doi:10.1055/s-0042-107598 · PMID:27224266
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13. Spinosi V, Semprini P, Langella V, et al. Presence of chemical additives and microbial inhibition capacity in grapefruit seed extracts used in apiculture. Vet Ital. 2007;43(1):109-13. · PMID:20411504
14. Avula B, Dentali S, Khan IA. Simultaneous identification and quantification by liquid chromatography of benzethonium chloride, methyl paraben and triclosan in commercial products labeled as grapefruit seed extract. Pharmazie. 2007;62(8):593-6. · PMID:17867553
15. Brandin H, Myrberg O, Rundlöf T, et al. Adverse effects by artificial grapefruit seed extract products in patients on warfarin therapy. Eur J Clin Pharmacol. 2007;63(6):565-70. doi:10.1007/s00228-007-0289-1 · PMID:17468864
16. Mandadi KK, Jayaprakasha GK, Bhat NG, et al. Red Mexican grapefruit: a novel source for bioactive limonoids and their antioxidant activity. Z Naturforsch C J Biosci. 2007;62(3-4):179-88. doi:10.1515/znc-2007-3-405 · PMID:17542482
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18. Ganzera M, Aberham A, Stuppner H. Development and validation of an HPLC/UV/MS method for simultaneous determination of 18 preservatives in grapefruit seed extract. J Agric Food Chem. 2006;54(11):3768-72. doi:10.1021/jf060543d · PMID:16719494
19. Sakamoto S, Sato K, Maitani T, et al. [Analysis of components in natural food additive "grapefruit seed extract" by HPLC and LC/MS]. Eisei Shikenjo Hokoku. 1996(114):38-42. · PMID:9037863
20. Takeoka G, Dao L, Wong RY, et al. Identification of benzethonium chloride in commercial grapefruit seed extracts. J Agric Food Chem. 2001;49(7):3316-20. doi:10.1021/jf010222w · PMID:11453769
21. Takeoka GR, Dao LT, Wong RY, et al. Identification of benzalkonium chloride in commercial grapefruit seed extracts. J Agric Food Chem. 2005;53(19):7630-6. doi:10.1021/jf0514064 · PMID:16159196
22. Bekiroglu S, Myrberg O, Ostman K, et al. Validation of a quantitative NMR method for suspected counterfeit products exemplified on determination of benzethonium chloride in grapefruit seed extracts. J Pharm Biomed Anal. 2008;47(4-5):958-61. doi:10.1016/j.jpba.2008.03.021 · PMID:18456447
23. U.S. Food and Drug Administration. Safety and Effectiveness of Consumer Antiseptics; Topical Antimicrobial Drug Products for Over-the-Counter Human Use. Final rule. Federal Register. 2016;81(172):61106-61130 (triclosan among 19 ingredients not generally recognized as safe and effective for consumer antiseptic washes; benzalkonium chloride, benzethonium chloride and chloroxylenol deferred).
24. Axe J. 10 Toxic Household Products (You Should Banish from Your Home). The Dr. Josh Axe Show. 2018 (number 2, antibacterial chemicals; YouTube upload https://www.youtube.com/watch?v=qrBm62PBuWQ).
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26. Komura M, Suzuki M, Sangsriratanakul N, et al. Inhibitory effect of grapefruit seed extract (GSE) on avian pathogens. J Vet Med Sci. 2019;81(3):466-472. doi:10.1292/jvms.18-0754 · PMID:30713281
27. Tsutsumi-Arai C, Takakusaki K, Arai Y, et al. Grapefruit seed extract effectively inhibits the Candida albicans biofilms development on polymethyl methacrylate denture-base resin. PLoS One. 2019;14(5):e0217496. doi:10.1371/journal.pone.0217496 · PMID:31136636
28. La Mantia I, Ciprandi G, Varricchio A, et al. Salso-bromo-iodine thermal water: a nonpharmacological alternative treatment for postnasal drip-related cough in children with upper respiratory tract infections. J Biol Regul Homeost Agents. 2018;32(1 Suppl. 2):41-47. · PMID:29450988
29. Oyelami OA, Agbakwuru EA, Adeyemi LA, et al. The effectiveness of grapefruit (Citrus paradisi) seeds in treating urinary tract infections. J Altern Complement Med. 2005;11(2):369-71. doi:10.1089/acm.2005.11.369 · PMID:15865506
30. Brzozowski T, Konturek PC, Drozdowicz D, et al. Grapefruit-seed extract attenuates ethanol-and stress-induced gastric lesions via activation of prostaglandin, nitric oxide and sensory nerve pathways. World J Gastroenterol. 2005;11(41):6450-8. doi:10.3748/wjg.v11.i41.6450 · PMID:16425415
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32. Heggers JP, Cottingham J, Gusman J, et al. The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity. J Altern Complement Med. 2002;8(3):333-40. doi:10.1089/10755530260128023 · PMID:12165191
33. Cao S, Xu W, Zhang N, et al. A mitochondria-dependent pathway mediates the apoptosis of GSE-induced yeast. PLoS One. 2012;7(3):e32943. doi:10.1371/journal.pone.0032943 · PMID:22403727
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35. Bailey DG, Dresser G, Arnold JM. Grapefruit-medication interactions: forbidden fruit or avoidable consequences? CMAJ. 2013;185(4):309-16. doi:10.1503/cmaj.120951 · PMID:23184849
36. Paine MF, Widmer WW, Hart HL, et al. A furanocoumarin-free grapefruit juice establishes furanocoumarins as the mediators of the grapefruit juice-felodipine interaction. Am J Clin Nutr. 2006;83(5):1097-105. doi:10.1093/ajcn/83.5.1097 · PMID:16685052
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Dr. Josh Axe, DC, DNM, CNS

Doctor of Natural Medicine · Founder, DrAxe.com

Dr. Axe is a certified doctor of natural medicine, clinical nutritionist, and multiple New York Times bestselling author. He has spent 20+ years in clinical practice helping people heal at the root cause and founded one of the most-visited natural-health platforms in the world.

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