Evening Primrose Oil
Research reviewed: Up until 03/2026
Evening Primrose Oil (Oenothera biennis seed oil) is a dietary supplement with 8 published peer-reviewed studies involving 1,680 participants, researched for Skin Health, PMS & Menopause, Breast Pain and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Skin Health
ModeratePMS & Menopause
StrongBreast Pain
ModerateRheumatoid Arthritis
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Skin Health
To evaluate evening primrose oil (EPO) for atopic eczema.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate evening primrose oil (EPO) for atopic eczema.
Dose
500 mg/day EPO (6% GLA)
Participants
99 patients with atopic eczema
Duration
20 weeks
Results
EPO significantly improved overall eczema severity, reducing itch, redness, and scaling compared to placebo. Red blood cell GLA levels increased proportionally to improvement in skin symptoms.
How They Measured It
Overall severity score, itch, redness, scaling
To evaluate EPO supplementation for atopic eczema.
Study Type
Meta-analysis
Purpose
To evaluate EPO supplementation for atopic eczema.
Dose
Various EPO doses
Participants
Pooled from 9 controlled trials (>700 patients)
Duration
Various
Results
EPO showed significant overall improvement in atopic eczema in meta-analysis. Subgroup analyses showed particularly strong effects on itch and skin inflammation. Quality of evidence varies across trials.
How They Measured It
Pooled symptom severity across RCTs
PMS & Menopause
To evaluate EPO on premenstrual syndrome symptoms.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate EPO on premenstrual syndrome symptoms.
Dose
3 g/day EPO
Participants
120 women with PMS
Duration
6 months
Results
EPO significantly reduced breast pain, mood disturbances, and water retention in PMS. The effect was attributed to GLA-derived prostaglandin E1 which modulates hormonal responses.
How They Measured It
PMS symptom diary, pain VAS, psychological symptoms
To assess EPO supplementation on hot flushes in menopausal women.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess EPO supplementation on hot flushes in menopausal women.
Dose
500 mg EPO twice daily
Participants
56 postmenopausal women with hot flushes
Duration
6 weeks
Results
EPO significantly reduced hot flush frequency and severity compared to placebo. Kupperman Index scores improved. EPO appears to reduce the intensity rather than frequency of menopausal flushing.
How They Measured It
Hot flush frequency and severity (diary), Kupperman Index
Breast Pain
To evaluate EPO for mastalgia (breast pain) in premenopausal women.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate EPO for mastalgia (breast pain) in premenopausal women.
Dose
3 g/day EPO
Participants
200 women with cyclical mastalgia
Duration
6 months
Results
EPO significantly reduced cyclical breast pain severity compared to placebo. Approximately 45% of EPO-treated women experienced significant symptom relief. The response rate was lower for non-cyclical mastalgia.
How They Measured It
Cardiff Breast Pain chart, pain VAS, breast tenderness score
Rheumatoid Arthritis
To assess EPO supplementation on symptoms and medication use in rheumatoid arthritis.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess EPO supplementation on symptoms and medication use in rheumatoid arthritis.
Dose
6 g/day EPO (540 mg/day GLA)
Participants
94 patients with rheumatoid arthritis
Duration
12 months
Results
EPO significantly reduced morning stiffness and joint tenderness. NSAID use was significantly reduced in the EPO group. The anti-inflammatory mechanism is via GLA-derived dihomo-GLA.
How They Measured It
Morning stiffness duration, joint tenderness, NSAID use
To evaluate EPO and other GLA sources for rheumatoid arthritis.
Study Type
Systematic review
Purpose
To evaluate EPO and other GLA sources for rheumatoid arthritis.
Dose
Various
Participants
Multiple RCT populations
Duration
Various
Results
EPO and borage oil (high GLA) supplementation consistently reduced joint tenderness and morning stiffness in RA. Higher GLA content sources showed greater effects. Well tolerated compared to standard disease-modifying drugs.
How They Measured It
Review of RCTs on joint symptoms, medication use, disease activity scores
To investigate EPO on prostaglandin profiles and joint inflammation in adjuvant-induced arthritis.
Study Type
Animal study
Purpose
To investigate EPO on prostaglandin profiles and joint inflammation in adjuvant-induced arthritis.
Dose
1 mL/kg/day EPO
Participants
Sprague-Dawley rats
Duration
21 days
Results
EPO supplementation significantly reduced joint swelling and shifted prostaglandin profiles from pro-inflammatory PGE2 to anti-inflammatory PGE1. Paw oedema was reduced by 62% compared to control.
How They Measured It
Joint swelling, PGE2 and PGE1 levels, paw weight
Frequently Asked Questions
Common questions about Evening Primrose Oil research
There are currently 10 peer-reviewed studies on Evening Primrose Oil (Oenothera biennis seed oil), involving 1,680 total participants. Research covers Skin health (eczema), PMS & menopause, Breast pain and 1 more areas. The overall evidence strength is rated as Very Strong.
The evidence is currently rated as "Very Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (7 human studies, 1 animal study), and reported outcomes.
Evening Primrose Oil has been researched for: Skin health (eczema), PMS & menopause, Breast pain, Rheumatoid arthritis. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 7 out of 10 studies are human trials. The remaining 1 is an animal study. Human trials carry more weight in our evidence scoring system.
Similar Supplements
Other supplements researched for similar health goals
