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Evening Primrose Oil

source of gamma-linolenic acid (GLA)

supplement
Evidence · Grade C
Meta-analysis availableSystematic review availableHuman trial evidenceTraditional useInteraction risk

GLA-rich oil for hormonal balance, skin, and breast tenderness.

Evening Primrose Oil (EPO) is derived from the seeds of the evening primrose plant (Oenothera biennis). It is a rich source of gamma-linolenic acid (GLA), an omega-6 fatty acid. GLA is an essential fatty acid that the body converts into substances that may help regulate inflammation and support cellular function. Due to its GLA content, EPO has been explored for various health conditions, particularly those involving inflammatory processes or hormonal imbalances. While it is a popular supplement, the scientific evidence supporting many of its purported benefits is limited and often inconclusive, with a need for more robust research.

Quick answer

What it is: Evening Primrose Oil (EPO) is derived from the seeds of the evening primrose plant (Oenothera biennis).

May support:Eczema (Atopic Dermatitis), PMDD, PMS, Psoriasis, Perimenopause, Menopause, Acne, Eczema (Atopic Dermatitis)

Evidence:Evidence · Grade C

Evidence Summary

Evidence · Grade C

Given the absence of specific PubMed studies provided, the evidence for Evening Primrose Oil's efficacy for various conditions is generally considered limited. Much of the existing research consists of small-scale studies, older trials, or studies with methodological limitations. There is a recognized need for more large-scale, well-designed, placebo-controlled clinical trials to definitively establish its benefits.

Last reviewed · Jun 2026

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Why It Works

Anti-inflammatory eicosanoids from GLA.

How it works in more detail

Gamma-linolenic acid (GLA) is an omega-6 fatty acid that, once ingested, is converted by the enzyme delta-6-desaturase into dihomo-gamma-linolenic acid (DGLA). DGLA can then be metabolized into various eicosanoids. Specifically, DGLA can be converted into prostaglandin E1 (PGE1), which is known for its anti-inflammatory, vasodilatory, and anti-aggregatory properties. DGLA can also compete with arachidonic acid (AA) for cyclooxygenase and lipoxygenase enzymes, potentially reducing the production of pro-inflammatory eicosanoids derived from AA, such as prostaglandin E2 (PGE2) and leukotriene B4 (LTB4). This competitive inhibition may contribute to its observed anti-inflammatory effects.

How to use

Always consult a qualified clinician.

Editorial guidance

Suggested dosage
500–1500 mg/day
Research dosage range
Studies have used a wide range of dosages, often between 1 gram to 6 grams of Evening Primrose Oil daily, with GLA content varying per product.
Typical onset
Effects, if any, may not be immediate and could take several weeks to months of consistent use to become noticeable, particularly for conditions like skin health or hormonal symptoms.
Typical forms
Capsule, Softgel
Quality markers
Look for products standardized for GLA content, typically around 8-10%. Choose cold-pressed, hexane-free oils to ensure purity. Reputable brands often provide third-party testing for contaminants and potency.
Medication interactions
  • Anticoagulant/Antiplatelet drugs (may increase bleeding risk)
  • Phenothiazines (may increase seizure risk)
Avoid if
  • Bleeding disorders
  • Scheduled for surgery (discontinue prior)
  • History of seizures (use with caution)

Community tips

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Suggested dosage

500–1500 mg/day

General guidance — discuss specifics with a clinician.

Active medicinal compounds

Gamma-linolenic acid (GLA), Linoleic acid (LA)

Traditional use

Historically, Native Americans used the evening primrose plant for various purposes, including as a poultice for bruises and skin problems, and as an internal remedy for digestive issues, sore throats, and general pain. The oil's use in modern herbalism largely stems from its GLA content.

Safety

Safety warnings

May lower seizure threshold.

Avoid if

  • Bleeding disorders
  • Scheduled for surgery (discontinue prior)
  • History of seizures (use with caution)

Medication interactions

  • Anticoagulant/Antiplatelet drugs (may increase bleeding risk)
  • Phenothiazines (may increase seizure risk)

Reported side effects

  • Mild gastrointestinal upset
  • Nausea
  • Diarrhea
  • Headache

General guidance — discuss specifics with a clinician.

Evidence ecosystem

Scientific literature, clinical guidance, government sources, ongoing research, traditional use, and lived experience — grouped by source type and quality.

Overall grade (C)

Given the absence of specific PubMed studies provided, the evidence for Evening Primrose Oil's efficacy for various conditions is generally considered limited. Much of the existing research consists of small-scale studies, older trials, or studies with methodological limitations. There is a recognized need for more large-scale, well-designed, placebo-controlled clinical trials to definitively establish its benefits.

Filter by source type

Meta-Analyses(1)

Pooled analyses across multiple human trials.

Very High Quality

  • A Systematic Review and Meta-Analysis of the Efficacy of Evening Primrose Oil for Mastalgia Treatment.

    Ahmad Adni LL, Norhayati MN, Mohd Rosli RR, Muhammad J · International journal of environmental research and public health · 2021

    Mastalgia, or breast pain, is common among women which can lead to significant impairment in daily living. Hence, finding an effective treatment that can alleviate the symptom is very important. Thus, we carry out this study to determine the efficacy of evening primrose oil (EPO) for mastalgia treatment in women. The review included published randomised clinical trials that evaluated EPO used for treating mastalgia against a placebo or other treatments, irrespective of the blinding procedure, publication status, or sample size. Two independent authors screened the titles and abstracts of the identified trials; full texts of relevant trials were evaluated for eligibility. Two reviewers independently extracted data on the methods, interventions, outcomes, and risk of bias. The random-effects model was used for estimating the risk ratios and mean differences with 95% confidence intervals. Thirteen trials with 1752 randomised patients were included. The results showed that EPO has no diffe

    Meta-AnalysisPubMedVery High Quality

Systematic Reviews(3)

Structured reviews of the full body of evidence (incl. Cochrane).

Very High Quality

  • Chronic fatigue syndrome.

    Reid S, Chalder T, Cleare A, Hotopf M, Wessely S · BMJ clinical evidence · 2011

    Chronic fatigue syndrome (CFS) affects between 0.006% and 3% of the population depending on the criteria of definition used, with women being at higher risk than men. We conducted a systematic review and aimed to answer the following clinical question: What are the effects of treatments for chronic fatigue syndrome? We searched: Medline, Embase, The Cochrane Library, and other important databases up to March 2010 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). We found 46 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. In this systematic review we present information relating to the effectiveness and safety of the followin

    Systematic ReviewPubMedVery High Quality

  • Chronic fatigue syndrome.

    Reid SF, Chalder T, Cleare A, Hotopf M, Wessely S · BMJ clinical evidence · 2008

    Chronic fatigue syndrome (CFS) affects between 0.006% and 3% of the population depending on the criteria of definition used, with women being at higher risk than men. We conducted a systematic review and aimed to answer the following clinical question: What are the effects of treatments for chronic fatigue syndrome? We searched: Medline, Embase, The Cochrane Library, and other important databases up to September 2007 (BMJ Clinical evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). We found 45 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. In this systematic review we present information relating to the effectiveness and safety of the

    Systematic ReviewPubMedVery High Quality

  • Premenstrual syndrome.

    Kwan I, Onwude JL · BMJ clinical evidence · 2007

    Premenstrual symptoms occur in 95% of women of reproductive age. Severe, debilitating symptoms (PMS) occur in about 5% of those women. There is no consensus on how symptom severity should be assessed, which has led to a wide variety of symptoms scales, making it difficult to synthesise data on treatment efficacy. The cyclical nature of the condition also makes it difficult to conduct RCTs. We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of drug treatments; hormonal treatments; psychological interventions; physical therapies; dietary supplements; and surgical treatments in women with premenstrual syndrome? We searched: Medline, Embase, The Cochrane Library and other important databases up to November 2006 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (

    Systematic ReviewPubMedVery High Quality

Observational Studies(2)

Cohort, case-control, and cross-sectional human studies.

Moderate Quality

  • Gynecology: select topics.

    Sidani M, Campbell J · Primary care · 2002

    Menopause, premenstrual syndrome, dysmenorrhea, female fertility, and mastalgia are common problems not easily treated by conventional medicine. Women often seek alternative therapies to help address these conditions. Some evidence points to the efficacy of black cohosh, exercise, and possibly Kava and St. John's wort, in the treatment of menopausal symptoms. Clinical trials indicate that symptoms of premenstrual syndrome may be alleviated with calcium, magnesium, vitamin E. Thiamine, omega-3 fatty acids, the Japanese herbal concoction, TSS, and calcium have proved useful in treating women with dysmenorrhea. Symptoms of mastalgia may be attenuated by evening primrose oil, chaste tree and flaxseed oil may be helpful.

    Observational StudyPubMedLow Quality

  • Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions.

    Miller LG · Archives of internal medicine · 1998

    Herbal medicinals are being used by an increasing number of patients who typically do not advise their clinicians of concomitant use. Known or potential drug-herb interactions exist and should be screened for. If used beyond 8 weeks, Echinacea could cause hepatotoxicity and therefore should not be used with other known hepatoxic drugs, such as anabolic steroids, amiodarone, methotrexate, and ketoconazole. However, Echinacea lacks the 1,2 saturated necrine ring associated with hepatoxicity of pyrrolizidine alkaloids. Nonsteroidal anti-inflammatory drugs may negate the usefulness of feverfew in the treatment of migraine headaches. Feverfew, garlic, Ginkgo, ginger, and ginseng may alter bleeding time and should not be used concomitantly with warfarin sodium. Additionally, ginseng may cause headache, tremulousness, and manic episodes in patients treated with phenelzine sulfate. Ginseng should also not be used with estrogens or corticosteroids because of possible additive effects. Since the

    Observational StudyPubMedLow Quality

Clinical Trial Registries(2)

Registered ongoing or completed trials (ClinicalTrials.gov).

Moderate Quality

Limitations: The primary limitation is the lack of robust, high-quality clinical trials. Many studies are small, have short durations, or lack adequate control groups. Inconsistent findings across studies also contribute to the uncertainty regarding its efficacy. The absence of specific studies for this entry further highlights the gap in readily available, strong evidence.

This page is educational. Statements use phrases like "may support" and "has been studied for"because no remedy here is approved to cure, treat, or reverse any condition. Discussion happens on the ailment pages — community statistics here are derived from those reports. Always consult a qualified clinician.

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