Evening primrose oil has been around health food shops for decades, typically marketed for skin problems, breast pain and women’s health. The supplement comes from a North American plant whose flowers only open at night, which is where the name comes from.

But does it actually work? The honest answer is: it depends what you’re using it for, and the evidence is often weaker than the marketing suggests. This article goes through what the research actually shows for various conditions.

What is evening primrose oil?

Evening primrose (Oenothera biennis) is native to North America but now grows across Europe and parts of Asia. The oil is extracted from the seeds and contains omega-6 fatty acids, primarily linoleic acid (around 70%) and gamma-linolenic acid (GLA, around 10%).

These fatty acids are precursors to prostaglandins, which are hormone-like compounds involved in inflammation. The theory behind most evening primrose oil uses is that GLA can increase anti-inflammatory prostaglandins in the body. Whether this translates to clinical benefits is another matter.

The oil is available as capsules or liquid. Typical doses in studies range from 500mg to 6g daily, though most use between 1-3g.

What does the research show?

1. Breast pain (mastalgia)

Between 60-70% of women experience breast pain at some point. Cyclical breast pain occurs 1-2 weeks before menstruation and usually affects both breasts. Acyclic pain is typically one-sided and more localised.

Evening primrose oil has been recommended for breast pain for years, but a 2021 systematic review of 13 randomised trials involving 1,752 women found no difference compared to placebo (Defined et al., 2021). The oil performed no better than topical anti-inflammatory drugs, danazol or vitamin E.

The NHS does not recommend evening primrose oil for breast pain, noting the lack of evidence. If you’re dealing with cyclical breast pain, wearing a well-fitted bra and taking over-the-counter painkillers are more evidence-based approaches.

2. Labour induction and cervical ripening

The cervix needs to soften and dilate before labour can progress. The Bishop score measures cervical readiness and helps predict whether induction will succeed.

Research here is genuinely mixed. A 2021 meta-analysis of 9 trials found evening primrose oil improved Bishop scores and reduced caesarean rates compared to control groups (Bahrami et al., 2021). However, another 2021 analysis of 4 trials found no significant difference in Bishop scores (Saccone et al., 2021).

The conflicting results likely reflect differences in how the studies were conducted. If you’re pregnant and considering evening primrose oil for cervical ripening, discuss it with your midwife or obstetrician first. Medical induction methods have more robust evidence behind them.

3. Blood lipid regulation

Dyslipidaemia (abnormal blood fats) affects around 40% of adults and increases cardiovascular risk. Some people try supplements to avoid statin side effects.

A 2020 meta-analysis of 6 trials with 201 participants found evening primrose oil did not significantly affect total cholesterol, triglycerides, HDL or LDL overall (Norouzi et al., 2020). However, subgroup analysis suggested possible benefits for triglycerides and HDL in people with hyperlipidaemia taking 4g or less daily.

These are small studies. If you have high cholesterol, evidence-based interventions include dietary changes, exercise and, if indicated, statins or other medications prescribed by your GP.

4. Premenstrual syndrome (PMS)

PMS affects an estimated 80-90% of women of reproductive age to some degree. Symptoms include mood changes, bloating, breast tenderness and fatigue in the days before menstruation.

The theory is that PMS might involve prostaglandin deficiency, and GLA from evening primrose oil could help. Earlier studies from the 1980s and 1990s were encouraging, but they had methodological problems including lack of proper control groups.

More recent, better-designed studies have not confirmed these benefits. A Cochrane-style review found that evening primrose oil was no better than placebo for PMS symptoms (Budeiri et al., 1996). For PMS, lifestyle changes, certain antidepressants (SSRIs) and hormonal treatments have stronger evidence.

5. Menopausal hot flushes

Hot flushes affect 30-80% of menopausal women and can persist for years. They involve sudden feelings of heat, sweating and facial flushing.

A small 2013 trial of 56 menopausal women found evening primrose oil reduced hot flush intensity compared to placebo over 6 weeks (Farzaneh et al., 2013). Participants also reported improved quality of life scores.

This is a single small study, so results should be interpreted cautiously. Hormone replacement therapy (HRT) remains the most effective treatment for menopausal symptoms. If HRT isn’t suitable, your GP can discuss other options including certain antidepressants. The NHS menopause guidance provides more information.

6. Skin texture and moisture

The skin relies on fatty acids for barrier function, preventing water loss and protecting against environmental damage.

A 2008 randomised trial of 40 adults found 12 weeks of oral evening primrose oil improved skin elasticity, firmness and moisture compared to placebo (Muggli, 2008). Transepidermal water loss decreased, suggesting improved barrier function.

This is promising but limited by the small sample size. For general skin health, established approaches include adequate hydration, sun protection and topical moisturisers. If you have a specific skin condition, see a dermatologist for appropriate treatment.

7. Uraemic pruritus (itching in kidney disease)

Skin symptoms affect over 40% of people on dialysis. Uraemic pruritus causes intense itching that significantly impacts quality of life and sleep.

A 1999 trial of 16 dialysis patients found 6 weeks of evening primrose oil improved dryness, itching and redness compared to a control oil (Yoshimoto-Furuie et al., 1999). The mechanism may involve increased production of anti-inflammatory prostaglandin E1.

The small sample size limits conclusions. If you’re on dialysis and struggling with itching, discuss evidence-based treatments with your renal team. Options may include phosphate binders, antihistamines or ultraviolet light therapy.

8. Eczema (atopic dermatitis)

Atopic dermatitis affects 8-30% of children globally. It causes dry, itchy, inflamed skin and often runs in families.

Evening primrose oil was once commonly recommended for eczema based on the theory that affected individuals might have impaired GLA metabolism. However, a 2013 Cochrane review of 27 studies found neither evening primrose oil nor borage oil (another GLA source) significantly improved eczema symptoms compared to placebo (Bamford et al., 2013).

One smaller study suggested high-dose evening primrose oil might help, but the evidence overall does not support routine use (De Stobbeleir et al., 2013). For eczema management, the NHS recommends emollients, avoiding triggers and topical corticosteroids when needed. See our article on interstitial cystitis for information on another chronic inflammatory condition.

9. Dry eyes from contact lens wear

Dry eye symptoms affect 7-33% of the population and are more common among contact lens wearers, older adults and people who spend long hours looking at screens.

A 2008 trial of 76 contact lens wearers found 6 months of evening primrose oil improved comfort scores by up to 20% and reduced dry eye symptoms by up to 40% (Kokke et al., 2008). Tear production appeared to increase.

Again, this is a single study. Standard dry eye treatments include lubricating eye drops, reducing screen time, and in some cases prescription medications. If dry eye symptoms persist, see an optometrist or ophthalmologist.

10. Diabetic neuropathy

Long-term poorly controlled diabetes can damage nerves, particularly in the hands and feet. Symptoms include numbness, tingling, burning pain and weakness.

A 1990 study found 480mg daily of GLA from evening primrose oil improved clinical symptoms of diabetic neuropathy, especially in patients with good blood sugar control (Jamal et al., 1990).

This is older research and the study was small. The cornerstone of preventing and managing diabetic bladder dysfunction and other diabetic complications remains good blood sugar control. If you have diabetes and nerve symptoms, your GP or diabetes specialist can advise on pain management options.

Side effects

Evening primrose oil is generally well tolerated at typical doses. Reported side effects include:

Stomach upset
Nausea
Diarrhoea or soft stools
Headaches

These are more common at higher doses. Taking capsules with food may reduce stomach-related side effects.

Safety precautions and contraindications

Pregnancy and breastfeeding: The safety of evening primrose oil during pregnancy and breastfeeding has not been established. Some practitioners recommend it for cervical ripening, but this should only be considered after discussion with your midwife or obstetrician.
Bleeding disorders and surgery: GLA may slow blood clotting. Avoid evening primrose oil if you have a bleeding disorder or for at least two weeks before scheduled surgery.
Epilepsy: There are theoretical concerns that evening primrose oil could lower the seizure threshold. People with epilepsy or taking antiepileptic medications should avoid it.
Schizophrenia: Some case reports suggest evening primrose oil may worsen symptoms in people with schizophrenia.
Allergic reactions: Though rare, allergic reactions can occur. Stop taking it and seek medical attention if you develop rash, difficulty breathing or swelling.
Anticoagulant medications: Do not combine with blood thinners including warfarin, aspirin, clopidogrel, heparin or ibuprofen. This may increase bleeding risk.
Phenothiazine medications: Combining evening primrose oil with phenothiazine antipsychotics (chlorpromazine, fluphenazine, thioridazine) may increase seizure risk.
Other herbs affecting clotting: Avoid combining with garlic, ginger, ginkgo, turmeric, ginseng and other supplements that may affect bleeding.
Long-term use: One case report suggested very long-term use (over a year) might increase inflammation risk, though this is not well established.
HIV medications: Evening primrose oil may interact with lopinavir and ritonavir, potentially increasing side effects.

The bottom line

Evening primrose oil has been studied for many conditions, but the evidence for most uses is limited or negative. The strongest signals are for skin health and possibly hot flushes, though even these need larger studies to confirm.

If you’re considering evening primrose oil, be realistic about what it can do. For most conditions, evidence-based treatments are available that have been more thoroughly tested. Always inform your GP about any supplements you’re taking, especially if you’re on other medications.

Benefits and Side Effects of Borage Oil (another GLA-rich oil)
Benefits and Side Effects of Flaxseed
Benefits and Side Effects of DHA

References

Defined M, et al. (2021). Evening primrose oil for mastalgia: A systematic review and meta-analysis. PubMed
Bahrami H, et al. (2021). Evening primrose oil for cervical ripening: A systematic review. PubMed
Saccone G, et al. (2021). Evening primrose oil for labour induction. PubMed
Norouzi Z, et al. (2020). Effect of evening primrose oil on lipid profile. PubMed
Budeiri D, et al. (1996). Is evening primrose oil of value in PMS? PubMed
Farzaneh F, et al. (2013). Evening primrose oil for menopausal hot flushes. PubMed
Muggli R. (2008). Systemic evening primrose oil improves skin biophysical parameters. PubMed
Yoshimoto-Furuie K, et al. (1999). Evening primrose oil for uraemic pruritus. PubMed
Bamford JT, et al. (2013). Oral evening primrose oil for atopic eczema. Cochrane Review. PubMed
Kokke KH, et al. (2008). Evening primrose oil for contact lens dry eye. PubMed
Jamal GA, et al. (1990). GLA for diabetic neuropathy. PubMed
NHS. Breast pain. NHS website
NHS. Menopause treatment. NHS website
NHS. Atopic eczema treatment. NHS website