Evening Primrose (Oenothera biennis): Uses, Evidence and Safety
Evening primrose oil (Oenothera biennis seed oil): what NIH and EU regulators say about PMS, breast pain and skin, plus blood thinner, blood pressure and pregnancy cautions.
Content last updated . This page has not been medically reviewed.
Safety first. Natural products can cause side effects and interact with medicines. Read herb safety and interactions before you use anything on this page.
Uses studied and safety checks for Evening Primrose Oil
Read the safety checks first. Each card says whether a finding comes from people, from the lab or from tradition, which product and way of use was tested, and how strong the evidence is. A finding for one product or one way of using it does not carry over to another.
Check before you use (4)
- Pregnancy and breastfeeding caution. NCCIH says it may be safe in pregnancy and breastfeeding but evidence is not conclusive; breast milk GLA rises without a link to harm in infants. Memorial Sloan Kettering tells clinicians pregnant women should not take it and links it to labor abnormalities. A 2014 review reported severe adverse events in pregnancy.
- Bleeding risk and blood-thinning medicines. Memorial Sloan Kettering says the oil may increase bleeding risk, with possible added effects with anticoagulants and antiplatelet drugs such as warfarin. Tell the prescriber and surgical team.
- Blood pressure and HIV medicine (lopinavir). Memorial Sloan Kettering says the oil can raise blood pressure (linked to higher readings in a large population study) and may change how the HIV medicine lopinavir works, raising its levels.
- Side effects, product mix-ups and a lung case report. NCCIH says it is generally well tolerated; stomach upset, nausea and diarrhea are most common. The EU summary adds headache, rash and other allergic reactions. Memorial Sloan Kettering notes some products contain phytoestrogens and describes one case of lipoid pneumonia after long-term use, from oil entering the lungs.
Evening primrose oil and eczema (swallowed capsules)
Not enough evidenceA Cochrane review of 27 trials (1,596 people) found swallowed evening primrose oil and borage oil did not improve eczema symptoms more than placebo. NCCIH says the same.
Supplements: No benefit shown for eczema when swallowed.
Evening primrose oil and dry-skin itching (EU traditional use)
Not enough evidenceThe EU herbal committee accepts evening primrose oil for relief of itching in dry skin, on the basis of long traditional use. It says clinical evidence was insufficient, and the summary describes oral preparations for adults and teenagers over 12.
Supplements: Traditional-use listing only; see a doctor if symptoms last more than 8 weeks.
Evening primrose oil put on the skin
Not enough evidenceA 2024 review of trials reported better skin hydration and barrier function in healthy volunteers in some studies, but its abstract does not say how the oil was given. Proper evidence for oil applied to the skin was not found in the sources we read. Memorial Sloan Kettering says human evidence for skin conditions is limited and mixed.
Supplements: Not established. Do not assume results from capsules apply to skin products, or the reverse.
Evening primrose oil and breast pain (swallowed)
Not enough evidenceA 2021 meta-analysis of 13 trials (1,752 women) found evening primrose oil relieved breast pain about as well as placebo and other treatments. NCCIH says it is probably no better than placebo.
Supplements: No benefit over placebo shown.
Evening primrose oil and premenstrual syndrome (PMS)
Not enough evidenceNCCIH says there is not enough evidence to show whether it helps PMS. Memorial Sloan Kettering notes an analysis that did not find it effective.
Supplements: Not shown to help.
Evening primrose oil and menopause hot flashes (swallowed)
Preliminary or mixedA 2024 meta-analysis found hot-flash severity was lower than with placebo in courses under 6 months, but frequency and duration did not change. The authors called the evidence insufficient. NCCIH also says evidence is insufficient.
Supplements: Possible small effect on severity; not firmly established.
Evening primrose oil in late pregnancy and starting labor
Preliminary or mixedA 2023 meta-analysis of 9 studies reported higher cervix-ripening scores, fewer cesarean births and shorter labor stages, with high differences between studies. A 2018 placebo-controlled trial (80 first-time mothers at 40 weeks) found no difference in delivery timing, induction or labor length. NCCIH says results are inconsistent and long-term safety is not established.
Supplements: Inconsistent; use only under a midwife or doctor.
Seizures and epilepsy
Not enough evidenceA concern that the oil lowers seizure threshold dates from early-1980s reports. A 2007 review argues the link is spurious and that seizures should be dropped as a side effect. NCCIH and Memorial Sloan Kettering do not mention seizures. This is one author's argument, not a regulator's position.
Supplements: Unresolved; ask a clinician.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (3)
- Healthy SkinPreliminary or mixed
Oral evening primrose oil has not been shown to help eczema, and the EU accepts it only on traditional use for dry-skin itching. Skin-product evidence was not found in the sources we read.
- Menopause SupportPreliminary or mixed
A 2024 meta-analysis found lower hot-flash severity but no change in frequency or duration; evidence is insufficient.
- Women’s WellnessPreliminary or mixed
Used for PMS, breast pain, menopause symptoms and late pregnancy. Trials found no benefit for breast pain, none established for PMS, and mixed results for hot flashes and labor.
Body systems (5)
- Cardiovascular SystemDocumented risk
May increase bleeding risk with blood thinners and may raise blood pressure, according to Memorial Sloan Kettering.
- Integumentary SystemPreliminary or mixed
Oral evening primrose oil has not been shown to help eczema, and the EU accepts it only on traditional use for dry-skin itching. Skin-product evidence was not found in the sources we read.
- Reproductive HealthPreliminary or mixed
Studied for PMS, menopause hot flashes and cervix ripening at term, with mixed or no-benefit results and pregnancy cautions.
- Reproductive SystemPreliminary or mixed
Studied for PMS, menopause hot flashes and cervix ripening at term, with mixed or no-benefit results and pregnancy cautions.
- Skin, Hair & BeautyPreliminary or mixed
Oral evening primrose oil has not been shown to help eczema, and the EU accepts it only on traditional use for dry-skin itching. Skin-product evidence was not found in the sources we read.
Body parts (2)
- Reproductive OrgansPreliminary or mixed
Studies looked at the cervix in late pregnancy; results are inconsistent and the oil should be used only with a midwife or doctor.
- SkinPreliminary or mixed
Oral evening primrose oil has not been shown to help eczema, and the EU accepts it only on traditional use for dry-skin itching. Skin-product evidence was not found in the sources we read.
Root causes (1)
- Medication Side EffectsDocumented risk
May increase bleeding with blood thinners, may raise blood pressure, and may raise levels of the HIV medicine lopinavir.
Conditions & symptoms (1)
- Menopausal SymptomPreliminary or mixed
Hot-flash severity was lower than with placebo in a 2024 meta-analysis; frequency and duration did not change; evidence insufficient.
Safety first: bleeding, medicines and pregnancy
Memorial Sloan Kettering says evening primrose oil may increase bleeding risk with blood thinners such as warfarin, may raise blood pressure, and may affect how the HIV medicine lopinavir works. [1] Tell the prescriber, pharmacist and surgical team. See medicine interactions and supplements before surgery. Pregnancy advice differs between sources, covered below. Seizure risk is not described in the sources we read, so people with epilepsy should ask a clinician; see epilepsy and seizure risk with herbs and oils.What it is
Evening primrose is a plant native to North and South America, with yellow flowers that open at sunset. The supplement is an oil from the seeds, rich in omega-6 fatty acids including gamma-linolenic acid (GLA). [2] The accepted name is Oenothera biennis L., in the evening primrose family (Onagraceae). [3] The EU regulator also names Oenothera lamarckiana L. as a source of the oil. [4] This is an oil, not a leaf herb. For fatty acids see evening primrose, borage and GLA oils and omega fatty acids.Traditional use
NIH says Native Americans applied juices from the stem and leaves to the skin for inflammation, bruises and minor wounds, and used the leaves by mouth for gastrointestinal disorders and sore throats. [2] The oil used today is a different preparation from those juices and leaves, so these uses do not transfer to the oil. Tradition is not evidence that it works.What research shows
| Use | What the source found | Strength of evidence | Population and form studied |
|---|---|---|---|
| Any health condition | NIH: not enough evidence to support use for any health condition. [2] | Insufficient evidence | Adults; oral oil |
| Atopic dermatitis (eczema) | Oral oil has not been shown to help. [2] | No good evidence of benefit | Oral oil |
| Breast pain | Probably no better than placebo. [2] A 2021 meta-analysis of 13 trials (1752 women) found no difference versus placebo or other treatments. [5] | No good evidence of benefit | Women with mastalgia |
| PMS, menopause, rheumatoid arthritis | Insufficient evidence. [2] | Insufficient evidence | Mixed |
| Starting labor | Studies by mouth or vaginally had inconsistent results. [2] | Mixed | Pregnant women at term |
| Dry-skin itching, EU view | Accepted on traditional use only, with quality of evidence rated very low to moderate. [4] | Traditional use (regulatory) | Adults and adolescents over 12 |
Memorial Sloan Kettering says human studies for skin conditions are limited and mixed, and that some analyses did not find benefit for breast pain or PMS. [1] See herbs for menstrual cramps and PMS.
Forms
Evening primrose oil comes as softgels, capsules and liquids, and is added to skin creams. [1] Oral oil and skin products are different preparations, and the EU summary covers oil made by pressing or with a solvent, in solid forms by mouth. [4] Amounts are for a clinician or pharmacist to decide. The EU summary says to see a doctor if symptoms last longer than 8 weeks. [4]Safety details
- Common effects: abdominal pain, nausea, diarrhea, headache. [2][1] NIH says it is probably safe for most adults by mouth; less is known for children. [2]
- Bleeding: in a small study, bleeding time rose in 9 of 12 people taking GLA from evening primrose oil for several months. [1]
- Pregnancy: NIH says it may be safe in pregnancy and breastfeeding but the evidence is not conclusive, and long-term safety for starting labor has not been established. [2] Memorial Sloan Kettering says pregnant women should not take it because of reported labor complications. [1] Do not use it to try to start labor without a clinician.
- Breastfeeding: it raises GLA in breast milk without linked harm to the infant. [2]
- Hormone-sensitive cancers: the oil itself is not estrogenic, but some products add phytoestrogens, so use caution. [1]
- Rare: lipoid pneumonia in one woman after chronic use. [1]
- Liver and kidney disease, allergy: not described in the sources we read.
- Quality: see quality testing.
Frequently asked questions
Does evening primrose oil help PMS?
NIH found insufficient evidence for PMS. [2]
Does it help breast pain?
Probably no better than placebo, according to NIH. [2]
Does it help eczema?
NIH says oral evening primrose oil has not been shown to relieve atopic dermatitis. [2]
Is it safe with blood thinners?
Ask your prescriber or pharmacist; it may increase bleeding risk. [1]
Is it safe in pregnancy?
Sources differ: NIH says it may be safe but not conclusive, and Memorial Sloan Kettering says not to take it. [2][1]
References
- Memorial Sloan Kettering Cancer Center. Evening Primrose Oil: Purported Benefits, Side Effects and More. Read 2026-10-23.
- NCCIH, NIH. Evening Primrose Oil. Read 2026-10-23.
- GBIF Backbone Taxonomy. Oenothera biennis L.. Read 2026-10-23.
- European Medicines Agency, HMPC. Evening primrose oil: summary for the public, EMA/422144/2018. Read 2026-10-23.
- Ahmad Adni LL, et al. A systematic review and meta-analysis of the efficacy of evening primrose oil for mastalgia treatment. Int J Environ Res Public Health. 2021;18:6295. Read 2026-10-23.