GSE (Grapefruit Seed Extract)
Updated: 5 days ago
Grapefruit seed extract (GSE) is one of the most talked-about natural options for the hidden cyst forms of Lyme. Here's what Lyme-literate doctors and the research say, the good and the mixed, so you can talk it over with your doctor.
Short on time or energy? A quick-view graphic with the key points is at the bottom of this post.
Links to both strengths I mention are under FIND THE PRODUCTS.
Want to learn more about cyst forms and what else is used for them? See my posts:
CYST FORMS OF LYME
CYST FORMS OF LYME - POSSIBLE SOLUTIONS
MY EXPERIENCE
In the past, I used a few brands my Lyme-literate doctor recommended. I started with the lower strength (125 mg) and moved up to 250 mg twice a day, as directed by my doctor. Dr. Marty Ross suggests a similar amount. My doctor has also used GSE for SIBO.
WHAT IT IS
- An extract made from grapefruit seeds.
- Sold as capsules, and also as a liquid concentrate that must always be diluted.
- Lyme-literate doctors use it for the round-body (cyst) forms of Lyme, and some use it as a natural antifungal.
HOW LYME DOCTORS USE IT
- ILADS doesn't mention GSE. It explains that Lyme can change shape, go dormant, hide and form biofilms, and that treatment should be tailored to each person.
- Dr. Richard Horowitz uses GSE along with Plaquenil for the round-body forms, as part of his combination protocols. His 2022 to 2024 papers describe this in his own patients (chart reviews and case reports from his own practice, with no untreated or placebo group).
- Dr. Marty Ross lists GSE (250 mg, one capsule twice a day) among his options for cyst forms. In his experience it works about as well as the prescription cyst options and is easier to tolerate than Flagyl or Tindamax.
- Dr. Ross also lists GSE among the options for actively growing Lyme and Bartonella.
- Dr. Horowitz names GSE as one of the natural antifungals that can help with yeast when prescription antifungals don't work or can't be used. (Older source, 2020, still worth reading.)
WHAT RESEARCH SHOWS
- An older 2007 lab study using a European Lyme species found GSE broke open young cyst forms (all of them at the stronger strengths), killed the moving spiral forms, and, at the stronger strengths, kept them from turning into cysts. This was in a dish, not in people. The authors said studies in living bodies were still needed and suggested testing GSE together with antibiotics. (Older source, still worth reading.)
- Dr. Samuel Shor's 2023 review (he's a past ILADS president) points out that lab results on GSE and Lyme have been conflicting (see MORE RESEARCH WITH MIXED RESULTS below).
GOOD TO KNOW
- Read the warning on each bottle, and ask your doctor before starting, especially if you're pregnant or nursing.
- Product quality matters. A 2023 review by natural product experts explains that, since 1991, some products sold as "grapefruit seed extract" have been found to contain synthetic disinfectants, such as triclosan, benzethonium chloride and benzalkonium chloride.
- An older 1999 lab study found that the GSE products that killed germs all contained added preservatives, while extracts without them showed no activity. A newer 2021 lab study, using GSE that its maker confirmed was free of benzethonium chloride, did find activity against drug-resistant staph. (Both are older sources, still worth reading.)
- Choose a brand that is third-party tested for these chemicals. The Allergy Research Group products below say on the label that they are.
- Blood thinners: in an older 2007 report, a woman taking warfarin had a bruise and blood that became much too thin after a few days of GSE drops. The products tested contained the disinfectant benzethonium chloride and no real GSE. Ask your doctor first if you take a blood thinner. (Older source, still worth reading.)
- Medicines: the ParaMicrocidin label says to talk with your doctor before using it if you take any medication, are pregnant or nursing, or have a health condition.
MORE RESEARCH WITH MIXED RESULTS
- In an older 2020 Johns Hopkins lab study funded by Bay Area Lyme Foundation, a GSE product tested free of contaminants had little or no effect on the dormant form of the main U.S. Lyme species (most of the bacteria were still alive, about the same as with no treatment). The researchers think the 2007 study may have differed because it used a European species, an older version of the product, or a hidden contaminant, such as an added preservative. A second GSE brand they checked contained a disinfectant. (Older source, still worth reading.)
- Gut: a 2021 study found GSE slowed H. pylori, a stomach germ, in the lab. But in mice, adding GSE to a probiotic didn't help any more than the probiotic alone.
FIND THE PRODUCTS
Buy products on Fullscript for a 25% discount
Allergy Research Group ParaMicrocidin 125 mg
Allergy Research Group ParaMicrocidin 250 mg
RELATED POSTS
CYST FORMS OF LYME
CYST FORMS OF LYME - POSSIBLE SOLUTIONS
NATURAL ANTIBIOTICS
BIOFILMS EDUCATION
BIOFILMS - POSSIBLE SOLUTIONS
CANDIDA EDUCATION
CANDIDA - POSSIBLE SOLUTIONS
SIBO (SMALL INTESTINAL BACTERIAL OVERGROWTH)
SIBO - POSSIBLE SOLUTIONS
GUT HEALTH - POSSIBLE SOLUTIONS
MAINTAIN REMISSION / PREVENT RELAPSE - POSSIBLE SOLUTIONS
ANTIBIOTICS - WHY USING ONLY ONE IS NOT RECOMMENDED IN CHRONIC LYME
https://www.riseabovelyme.com/post/antibiotics-why-using-only-one-is-not-recommended-in-chronic-lyme
SOURCES
- ILADS, "Controversies and Challenges" (updated September 2026)
- Horowitz RI, Freeman PR, Antibiotics (2022)
- Horowitz RI, Fallon J, Freeman PR, Microorganisms (2023)
- Horowitz RI, Fallon J, Freeman PR, Microorganisms (2024)
- "The Use of Natural Bioactive Nutraceuticals in the Management of Tick-Borne Illnesses," Microorganisms (2023), Dr. Samuel Shor and Dr. Sunjya Schweig
- "Botanical Ingredient Forensics: Detection of Attempts to Deceive Commonly Used Analytical Methods for Authenticating Herbal Dietary and Food Ingredients and Supplements," Journal of Natural Products (2023)
- "Grapefruit Seed Extract as a Natural Derived Antibacterial Substance against Multidrug-Resistant Bacteria," Antibiotics (January 2021, older source)
- "In vitro and in vivo inhibition of Helicobacter pylori by Lactobacillus plantarum pH3A, monolaurin, and grapefruit seed extract," Food and Function (2021)
- Dr. Marty Ross, "A Lyme Disease Antibiotic Guide" (June 2024)
- Dr. Marty Ross, "Persister Lyme & Bartonella Options" (January 2023)
- Older source, still worth reading: LymeDisease.org, "The Importance of Looking at Parasites, Viruses, Yeast and Fungal Infections," Dr. Richard Horowitz (January 2020)
- Older source, still worth reading: "Evaluation of Natural and Botanical Medicines for Activity Against Growing and Non-growing Forms of B. burgdorferi," Frontiers in Medicine (2020)
- Older source, still worth reading: Bay Area Lyme Foundation, "Seven Herbal Medicines Are Capable of Killing Lyme Disease Bacteria, According to New Lab Study" (February 21, 2020)
- Older source, still worth reading: Brorson and Brorson, "Grapefruit seed extract is a powerful in vitro agent against motile and cystic forms of Borrelia burgdorferi sensu lato," Infection (2007)
- Older source, still worth reading: "Adverse effects by artificial grapefruit seed extract products in patients on warfarin therapy," European Journal of Clinical Pharmacology (2007)
- Older source, still worth reading: "Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained," Pharmazie (1999)
- Product labels on Fullscript (checked October 2026)
Disclaimer: Rise Above Lyme makes no claims about any possible benefit of using any product mentioned within this site. Always consult with your doctor before adding anything. The information shared is based on personal experience, years of accumulated researched resources from Lyme Literate doctors and polls conducted within Lyme groups from actual patient experience using these solution ideas.
Comments