Plant Profile

Evening Primrose

Compiled by the Omnia Sana editorial team from the plant database ·Last updated August 15, 2026

Oenothera biennis

Family: Onagraceae · Parts used: Seed oil · Also known as: Evening star, Sundrop, Fever plant

The complete database record: 2 documented constituents, 1 pharmacological action, 6 traditional / indicated uses, with 17 cited sources.

Botanical Description

Biennial herb (Onagraceae): a basal leaf rosette in the first year, followed in the second year by a stout, often reddish, erect flowering stem 30-150 cm tall. Leaves are alternate, lanceolate, with a prominent pale (often red-tinged) midrib and a wavy, untoothed margin. Large, fragrant, lemon-scented, four-petalled yellow flowers open in the evening and typically wilt by the following midday, followed by a narrow, cylindrical seed capsule.

Height: 30-150 cm (flowering stem, second year)

Habit: Biennial: first-year basal rosette, second-year erect flowering stem

Leaves: Alternate, lanceolate, wavy (untoothed) margin, prominent pale midrib

Flowers: Large, fragrant, lemon-scented, yellow, four-petalled, opening in the evening

Stem: Stout, often reddish, erect (second year)

Root: Taproot

Fruit: Narrow cylindrical seed capsule

Flowering Period: June-September

Habitat & Distribution

Native to eastern North America, widely naturalised across Europe, Asia and elsewhere on disturbed, sunny ground - waste places, roadsides, dunes and railway banks - as a hardy coloniser of poor, sandy or gravelly soils.

Harvesting

Mature seed capsules are harvested in late summer to autumn once dry and brown, and the tiny seeds are cold-pressed for their oil, the medicinal part. The first-year rosette leaves and young shoots have traditionally been used as food, but must never be gathered without certain identification given the deadly foxglove look-alike risk documented for this plant.^[14]

Parts: Seed

Season: Late summer to autumn

Key Constituents

Gamma-linolenic acid (GLA) and linoleic acid^{[1, 3, 5, 9, 12, 13]}

Omega-6 essential fatty acids of the seed oil; GLA is the constituent the supplement is taken for.

Gamma-linolenic acid (GLA)

Other seed-oil fatty acids and plant sterols^[12]

Minor lipid constituents.

Phytosterols

Pharmacological Actions

Emollient / skin-soothing^{[1, 5, 12]}

Skin hydration and barrier function in healthy skin

Traditional & Indicated Uses

Eczema^{[2, 10, 13]}Strong · 9/10

Eczema / atopic dermatitis - popularly used, but a Cochrane review found oral EPO is NOT effective

Evidence: 9

Label: Eczema

more plants for eczema →detailed sources →

Hot flashes^{[11, 12]}Good · 8/10

Menopausal hot flushes - some trial benefit reported

Evidence: 8

Label: Hot flashes

more plants for hot flashes →detailed sources →

Menopause^[11]Moderate · 5/10

Evidence: 5

Label: Menopause

more plants for menopause →detailed sources →

Pain (general)^{[7, 12, 16]}Strong · 9/10

Premenstrual syndrome and cyclical breast pain - some positive but inconsistent trial results (a recent RCT found evening primrose oil reduced cyclical breast-pain severity versus placebo, with a combination of EPO and vitamin E most effective)

Evidence: 9

Label: Pain (general)

more plants for pain (general) →detailed sources →

PMS / premenstrual syndrome^{[12, 16]}Good · 8/10

Evidence: 8

Label: PMS / premenstrual syndrome

more plants for pms / premenstrual syndrome →detailed sources →

Skin irritation^[12]Good · 7/10

inferred from emollient action

Evidence: 7

Label: Skin irritation

more plants for skin irritation →detailed sources →

Traditional Use & History

Evening primrose has a Native American tradition as a food and poultice plant, but its modern use is almost entirely as a dietary source of gamma-linolenic acid (GLA), an omega-6 fatty acid marketed for skin, hormonal and inflammatory complaints. Clinical trial evidence for these specific uses (eczema, PMS, menopause) is mixed to weak, and a Cochrane review found oral evening primrose oil is not effective for eczema.^{[2, 12, 13]}

Preparations

Cold-pressed seed oil (capsules)^{[5, 12]}

The standard commercial form, standardised for GLA content - the form used in most clinical trials.

Dosage

Seed oil^{[5, 12]}

Clinical trials evaluating evening primrose oil have most often used around 2-4 g of oil daily, taken for at least several weeks; evidence of benefit is inconsistent across most studied conditions. Educational reference only, not a prescription.

Safety, Cautions & Contraindications

Safety note^{[12, 13]}Info

Evidence is weak and largely negative: a Cochrane review concluded that oral evening primrose oil is not an effective treatment for eczema, and the broader trial literature is heterogeneous. Adverse effects are mild and mainly gastrointestinal.

Safety note^[13]Caution

May increase bleeding risk and has been reported to interact with warfarin; avoid concentrated/medicinal use in pregnancy unless advised by a clinician.

Dangerous Lookalikes

Digitalis Purpurea^{[14, 17]}Fatal

Confused Part: First-year basal rosette leaves gathered as an edible/medicinal; deadly foxglove forms a very similar first-year rosette.

Confusion Context: Evening primrose (Oenothera biennis) is a biennial whose first-year rosette leaves (and later shoots and flowers) are eaten and used. As Totally Wild UK warns, a beginner could confuse the first-year rosette with deadly foxglove (Digitalis purpurea), because they share a similar first-year 'tick list' - both form rosettes of soft, pointed, sometimes pink-tinged leaves. Foxglove is potentially fatal: its leaves contain cardiac glycosides that disturb the heart rhythm. Because the rosettes are alike before either plant flowers, this is a genuine and potentially deadly confusion.

Distinguishing Features: Leaf hairiness and margin: foxglove leaves are softly hairy and much wider with a clearly serrated (toothed) margin and a net of sunken veins. Evening primrose leaves are narrower, far less hairy, with only a wavy (not toothed) margin., Midrib: evening primrose has a distinctive prominent white/pale midrib, often red-tinged; foxglove has a greyer, downier leaf with net veins., Best practice: do not eat any rosette leaf unless you have confirmed evening primrose (ideally seeing the plant's later stem or flowers); if the leaf is broad, soft-hairy and toothed, treat it as foxglove.

Key Test: Compare the leaves. Narrow, nearly hairless leaves with a wavy margin and a bold white midrib = evening primrose. Broad, softly hairy leaves with a toothed (serrated) margin and net veins = foxglove - deadly, do not eat. If in any doubt, do not gather the rosette.

Reviewed By: Omnia Sana (owner-authorized)

Reviewed Date: 2026-07-07

Harvest Readiness

^[15]

Part: seed

Signals: Collect the seeds when the capsules ripen and dry on the second-year flowering stem, in late summer to autumn.

Basis: traditional

Source Quote: the seeds ripen from August to October

Species Confirmed: 1

Notes: PFAF (REF-3298); the seeds (source of the seed oil) ripen from August to October on the second-year flowering stem. Single lineage -> provisional. SAFETY: the first-year leaf rosette resembles the FATAL foxglove (Digitalis purpurea) rosette - relevant if leaves rather than seed are gathered; see Dangerous Lookalikes.

External Identifiers

GBIF ›Wikidata ›

References & Sources

Timoszuk, M., Bielawska, K. and Skrzydlewska, E (2018) 'Evening Primrose (Oenothera biennis) Biological Activity Dependent on Chemical Composition', Antioxidants, 7(8), pp. 108. doi:10.3390/antiox7080108 Meta-analysis / review
https://doi.org/10.3390/antiox7080108
Williams, H.C (2003) 'Evening primrose oil for atopic dermatitis', BMJ, 327(7428), pp. 1358-1359. doi:10.1136/bmj.327.7428.1358 Meta-analysis / review
https://doi.org/10.1136/bmj.327.7428.1358
Gad El-Hak, H.N., Kishk, S.M. and Abdelrazek, H.M.A (2024) 'Evening primrose oil enriched with gamma linolenic acid and D/L-alpha tocopherol acetate attenuated carbon tetrachloride-induced hepatic injury model in male rats via TNF-alpha, IL-1beta, and IL-6 pathway', Toxicology Mechanisms and Methods, 34(5), pp. 469-483. doi:10.1080/15376516.2023.2301357 Preclinical
https://doi.org/10.1080/15376516.2023.2301357
Mert, H., Irak, K., Cibuk, S., Yildirim, S. and Mert, N (2022) 'The effect of evening primrose oil (Oenothera biennis) on the level of adiponectin and some biochemical parameters in rats with fructose induced metabolic syndrome', Archives of Physiology and Biochemistry, 128(6), pp. 1539-1547. doi:10.1080/13813455.2020.1781900 Preclinical
https://doi.org/10.1080/13813455.2020.1781900
Farag, M.A., Reda, A., Nabil, M., Elimam, D.M. and Zayed, A (2023) 'Evening primrose oil: a comprehensive review of its bioactives, extraction, analysis, oil quality, therapeutic merits, and safety', Food & Function, 14(18), pp. 8049-8070. doi:10.1039/d3fo01949g Meta-analysis / review
https://doi.org/10.1039/d3fo01949g
Moradi, M., Niazi, A., Heydarian Miri, H. and Lopez, V (2021) 'The effect of evening primrose oil on labor induction and cervical ripening: A systematic review and meta-analysis', Phytotherapy Research, 35(10), pp. 5374-5383. doi:10.1002/ptr.7147 Meta-analysis / review
https://doi.org/10.1002/ptr.7147
Belch, J.J. and Hill, A (2000) 'Evening primrose oil and borage oil in rheumatologic conditions', The American Journal of Clinical Nutrition, 71(1 Suppl), pp. 352S-356S. doi:10.1093/ajcn/71.1.352s Meta-analysis / review
https://doi.org/10.1093/ajcn/71.1.352s
Kalati, M., Kashanian, M., Jahdi, F., Naseri, M. and others (2018) 'Evening primrose oil and labour, is it effective? A randomised clinical trial', Journal of Obstetrics and Gynaecology, 38(4), pp. 488-492. doi:10.1080/01443615.2017.1386165 Randomized trial
https://doi.org/10.1080/01443615.2017.1386165
Ide, T (2023) 'gamma-Linolenic Acid-Rich Oil- and Fish Oil-Induced Alterations of Hepatic Lipogenesis, Fatty Acid Oxidation, and Adipose Tissue mRNA Expression in Obese KK-Ay Mice', Journal of Oleo Science, 72(3), pp. 313-327. doi:10.5650/jos.ess22341 Preclinical
https://doi.org/10.5650/jos.ess22341
Vassilopoulou, E., Comotti, A., Douladiris, N., Konstantinou, G.N., Zuberbier, T., Alberti, I., Agostoni, C., Berni Canani, R., O'Mahony, L., Venter, C. and Milani, G.P (2024) 'A systematic review and meta-analysis of nutritional and dietary interventions in randomized controlled trials for skin symptoms in children with atopic dermatitis and without food allergy: An EAACI task force report', Allergy, 79(7), pp. 1708-1724. doi:10.1111/all.16160 Meta-analysis / review
https://doi.org/10.1111/all.16160
Rattanatantikul, T., Maiprasert, M., Sugkraroek, P. and Bumrungpert, A (2020) 'Efficacy and Safety of Nutraceutical on Menopausal Symptoms in Post-Menopausal Women: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial', Journal of Dietary Supplements, 19(2), pp. 168-183. doi:10.1080/19390211.2020.1853648 Randomized trial
https://doi.org/10.1080/19390211.2020.1853648
Sharifi, M., Nourani, N., Sanaie, S. and Hamedeyazdan, S (2024) 'The effect of Oenothera biennis (Evening primrose) oil on inflammatory diseases: a systematic review of clinical trials', BMC Complementary Medicine and Therapies. doi:10.1186/s12906-024-04378-5 Meta-analysis / review
https://doi.org/10.1186/s12906-024-04378-5
Bamford, J.T.M., Ray, S., Musekiwa, A., van Gool, C., Humphreys, R. and Ernst, E (2013) 'Oral evening primrose oil and borage oil for eczema', Cochrane Database of Systematic Reviews. doi:10.1002/14651858.CD004416.pub2 Meta-analysis / review
https://doi.org/10.1002/14651858.CD004416.pub2
Totally Wild UK 'Evening Primrose (Oenothera biennis) Identification'. Available at: https://totallywilduk.co.uk/2025/03/11/evening-primrose-identification/ Traditional / reference
https://totallywilduk.co.uk/2025/03/11/evening-primrose-identification/
Plants For A Future 'Oenothera biennis (Evening Primrose)'. Available at: https://pfaf.org/user/Plant.aspx?LatinName=Oenothera+biennis Traditional / reference
https://pfaf.org/user/Plant.aspx?LatinName=Oenothera+biennis
Kumari, J., Amrita, Sinha, A., Kumari, S., Biswas, P. and Poonam (2024) 'Effectiveness of Evening Primrose and Vitamin E for Cyclical Mastalgia: A Prospective Study', Cureus, 16(4). doi:10.7759/cureus.58055 Randomized trial
https://doi.org/10.7759/cureus.58055
Vithayathil, M.K. and Edwards, M (2016) 'Comfrey herbal remedy causing second-degree heart block: do not be outfoxed by digitalis', BMJ Case Reports, 2016, pp. bcr2016216995. doi:10.1136/bcr-2016-216995 Clinical study
https://doi.org/10.1136/bcr-2016-216995

Selected studies & references

ReviewA systematic review and meta-analysis of nutritional and dietary interventions in randomized controlled trials for skin symptoms in children with atopic dermatitis and without food allergy: An EAACI task force report source↗ (2024)

ReviewThe effect of Oenothera biennis (Evening primrose) oil on inflammatory diseases: a systematic review of clinical trials source↗ (2024)

ReviewEvening primrose oil: a comprehensive review of its bioactives, extraction, analysis, oil quality, therapeutic merits, and safety source↗ (2023)

ReviewThe effect of evening primrose oil on labor induction and cervical ripening: A systematic review and meta-analysis source↗ (2021)

ReviewEvening Primrose (Oenothera biennis) Biological Activity Dependent on Chemical Composition source↗ (2018)

ReviewOral evening primrose oil and borage oil for eczema source↗ (2013)

ReviewEvening primrose oil for atopic dermatitis source↗ (2003)

ReviewEvening primrose oil and borage oil in rheumatologic conditions source↗ (2000)

All 14 studies in the Knowledge Finder →

Educational use only. This profile summarises traditional and scientific sources for reference. It is not medical advice and not a substitute for a qualified practitioner. Some plants carry safety cautions and drug interactions - always check before use.
This profile is assembled automatically from the Omnia Sana plant database, which we curate by hand. How this site is built.

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