Evening primrose oil is best known for its applications such as atopic dermatitis, eczema and rheumatoid arthritis, and is also used for some women’s health conditions, including breast pain, menopause, and premenstrual symptoms.
In empirical medicine, is the use of evening primrose oil really beneficial? Are there any side effects of evening primrose oil? See text analysis for details
What is evening primrose oil?
Evening primrose is a plant native to North America (now widely distributed in Europe and parts of Asia), named because the flowers only bloom at night, and its roots and leaves are often used by European nobles as medicine, so it has the title of imperial panacea.
Modern research has found that evening primrose oil extracted from evening primrose seeds is rich in omega-6 fatty acids, such as linoleic acid (about 70%) and gamma-linolenic acid (about 10%).
These fatty acids contribute to the normal functioning of many tissues in the body because they are precursors of anti-inflammatory substances such as prostaglandins, cytokines, etc., and are therefore potentially helpful for various inflammatory diseases.
What are the proven benefits of evening primrose oil?
1. Evening primrose oil is good for breast pain
About 60% to 70% of women experience some degree of breast pain (Mastalgia), which can be broadly classified as cyclical or acyclic mastella.
Cyclic mammalgia usually occurs 1 to 2 weeks before menstruation, and the pain is usually diffuse and bilateral, with some radiating to the upper arm and armpits. One side may be more severe, gradually subside after menstruation, and tend to occur between the ages of 30 and 40.
Acyclic mammalgia is usually unilateral and is located in a specific quadrant of the mammary gland. Patients are usually between the ages of 40 and 50 and are usually perimenopausal. There are a variety of causes, including cysts, perimammitis ductitis, stretching of the Cooper’s suspensory ligament, traumatic fat necrosis, breast skin thrombophlebitis, diabetic mastopathy, and tumors.
A systematic literature review and meta-analysis (13 randomised clinical trials involving 1752 women with breast pain) found no difference in reducing breast pain compared with placebo, topical nonsteroidal anti-inflammatory drugs (NSAIDs), danazol, or vitamin E. Note 1
In addition, there was no clear difference in the number of patients who received pain relief compared to placebo or other treatments.
*Conclusion: There is no clear benefit of evening primrose oil in women with breast pain, but more studies are needed due to the high heterogeneity of the trials included
2. Evening primrose oil is beneficial for cervical maturation and labor induction
A prerequisite for successful vaginal delivery is cervical ripening, followed by softening and dilation of the cervix. It occurs gradually during labor and accelerates the onset of labor.
The Bishop score, which contains the four features of the cervix (cervical dilation, cervical disappearance, cervical position and consistency) and the location of the fetal delivery site, is the most commonly used scoring system for predicting success in induction of labour.
Stimulation of cervical maturation by medical and surgical methods can have adverse consequences, including bleeding during and after delivery, longer delivery times, fetal distress and injury, uterine rupture and retardation, chorioamnionitis, and increased mortality. Therefore, it is preferable to manage this issue safely and reliably during outpatient treatment.
A systematic literature review and meta-analysis (9 RCTs) found significant differences between evening primrose oil and control groups in BISHOP scores, reduced caesarean section rates, time to first stage of labour, and duration to second stage of labour (but no significant differences in birth weight and frequency of oxytocin induction). Note 1
Another systematic literature review and meta-analysis (including 4 randomized controlled trials) showed that there was no significant difference in mean Bishop scores between the intervention group (evening primrose oil) and the control group before and after the intervention. Note 2
*Conclusion: The efficacy of evening primrose oil for cervical maturation, reduction of caesarean section rate, and shortening of labour duration in pregnant women with term pregnancy remains controversial, and the high heterogeneity of the trials included is limited, and more high-quality studies with precise design are needed to further verify
3. Evening primrose oil is beneficial to blood lipid regulation
Dyslipidemia, a change in one or more lipid components, including total cholesterol, LDL cholesterol, triglycerides, and HDL cholesterol, is a major risk factor for cardiovascular disease.
It is estimated that dyslipidemia is prevalent in 40.38% of people aged 6 years and older, and 8% of children and adolescents aged 17 to 20 years.
A meta-analysis (6 randomized controlled trials, 201 participants) pointed out that, overall, evening primrose oil supplementation was not significantly helpful in reducing total cholesterol, triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol. Note 1
However, subgroup analysis found that the effects of lowering triglycerides and raising HDL cholesterol were seen in patients with daily doses ≤4 g and hyperlipidemia.
*Conclusion: Evening primrose oil supplementation may have a positive effect on blood lipid regulation, but due to the small sample size and heterogeneity between studies, more studies are still needed for further verification
4. Evening primrose oil improves premenstrual syndrome
Premenstrual syndrome, commonly known as premenstrual dystonia, refers to a variety of physical and psychological discomforts in the period leading up to menstruation, and it is estimated that about 80% to 90% of women of reproductive age have these difficulties.
There are still many theories about the causes of PMS, among which the more common is the first type of prostaglandin PGE1 deficiency, and prolactin is too high, and evening primrose oil rich in GLA (γ-linolenic acid), is found to increase PGE1 and inhibit Prolactin, so it is believed to improve PMS.
The literature points out that there are both positive and negative opinions about the effect of evening primrose oil in improving PMS, with earlier studies biased in favor (but most of these experiments had design flaws and lacked a control group), while recent studies confirmed that the effect was not superior to placebo, or only slightly improved. Note 1
*Conclusion: Up to now, there are no large-scale experiments that confirm that evening primrose oil can help improve PMS
5. Evening primrose oil improves menopause-related hot flashes
Hot flashes (hot flashes) is a rapid heat dissipation reaction of the human body, the main characteristics are a large amount of sweating, peripheral vasodilation, strong internal heat sensation, is a common phenomenon in menopausal women, the incidence of about 30% to 80%, usually lasting 1 year, but a few may be up to 10 years, causing serious interference with life and sleep quality.
A randomized, double-blind controlled study (6 weeks, 56 menopausal women) found that oral evening primrose oil reduced the intensity of hot flashes and red flashes and improved HFRDIS scores (particularly social activity, relationships with others, and sexual activity programs) compared with placebo. Note 2
*Conclusion: Evening primrose oil may have an improved effect on hot flashes associated with menopause in women, but more empirical evidence is needed
6. Evening primrose oil improves skin texture
The skin is the largest organ in the human body and acts as a barrier, preventing water loss, preventing harmful compounds or organisms from entering the environment, and providing protection from solar radiation.
Characterized by active lipid metabolism with a unique lipid structure, the skin is the source of a range of bioactive lipid mediators, it can also sense pain, temperature, and touch, help regulate body temperature, and mediate inflammation and immune responses.
A randomized, double-blind, placebo-controlled study (12 weeks, 40 adults) showed that oral evening primrose oil was helpful in improving skin biophysical parameters such as transepidermal water loss, firmness, elasticity, fatigue resistance, and roughness. Note 4
*Conclusion: Oral evening primrose oil may have a positive effect on skin condition improvement, but limited by the small sample size, more large trials are needed to support it
7. Evening primrose oil is beneficial for uremia skin symptoms
Uremic skin symptoms are a common complication of end-stage renal disease, affecting more than 40% of dialysis patients.
It is a chronic, unpleasant symptom that has a strong negative impact on the patient’s quality of life, often leading to insomnia and mood disorders.
Triggers may include uraemia-related abnormalities (particularly involving calcium, phosphorus, and parathyroid hormone metabolism), toxin accumulation, systemic inflammation, dry skin, and common comorbidities such as diabetes and viral hepatitis.
A randomized, double-blind controlled study (6 weeks, 16 dialysis patients) showed that oral administration of gamma-linolenic acid-rich evening primrose oil increased dihomo-gamma-linolenic acid (a precursor to anti-inflammatory prostaglandin E1) and improved uremia skin symptoms such as dryness, itching, and erythema compared with a control group using linoleic acid.Note 5
*Conclusion: Oral evening primrose oil may have a positive effect on improving uremia skin symptoms, but limited by small sample sizes, more studies are needed to support this
8. Evening primrose oil is good for eczema (atopic dermatitis)
Atopic dermatitis is the most common skin inflammatory disease in infants and young children, with a global prevalence of about 8% to 30%, and the most important cause is genetics, such as one parent who has suffered from eczema, the incidence of the next generation will increase by 3.4 times.
Other factors associated with atopic dermatitis are: household smoking habits, age, sex, nutritional status, number of siblings, lifestyle, dust mites, animal dander, mold, cockroaches, air pollution, air allergens, and climate.
A Cochrane Review (27 studies, 1596 participants) noted that neither evening primrose oil nor borage oil significantly improved symptoms of ectopic eczema compared with placebo. Note 6
Another controlled study (8 weeks, 40 patients with atopic dermatitis) showed that whether using high or low doses of evening primrose oil, both groups could increase blood levels of Gamma Linolenic Acid and improve the Eczema Area Severity Index, but the improvement was more significant in the high-dose group. Note 7
*Comment: There is insufficient evidence to support a significant benefit of evening primrose oil in atopic dermatitis, and more research is needed
9. Beneficial for dry eyes (caused by wearing contact lenses)
Dry eye is one of the fastest growing eye diseases, mainly caused by insufficient or poor quality tear production, often causing tingling and burning sensation in the eyes, and blurred vision that prevents attention from matters that require eyesight, and the prevalence of dry eye is estimated to be about 7.4% to 33.7% of the total population.
Dry eye is most common among the elderly (especially postmenopausal women), and other factors such as wearing contact lenses, drug use, and excessive viewing of computers and mobile phones may further trigger or aggravate dry eye symptoms.
A double-blind controlled study (6-month study of 76 patients with dry eye due to contact lens wear) found that taking evening primrose oil improved contact lens comfort (up to 20%) and reduced dry eye assessment scores (up to 40%). Note 8
The mechanism behind this is related to the increased tear production (measured by tear meniscus height) and anti-inflammatory effects of evening primrose oil.
*Comment: Evening primrose oil may help relieve dry eye symptoms caused by wearing contact lenses, but due to the small sample size, more studies are needed to further validate
10. Beneficial for diabetic neuropathy
Diabetes is a dangerous disease that has no obvious symptoms on the surface, but secretly destroys the body, and the most troublesome thing is that once long-term blood sugar control is poor (at least 10 years), it may cause three major complications, such as retinopathy, nephropathy and neuropathy.
Among them, neuropathy mostly appears in the fingers and toes, and in the early stage, you will feel soreness and other sensations, and in severe cases, even blowing the wind is painful, resulting in weakness of hands and feet, which seriously affects daily life.
In the study, gamma linolenic acid (GLA) in evening primrose (480 mg daily) was found to improve the clinical symptoms of diabetic neuropathy (including pain, weakness, etc.), especially in patients with good blood sugar control. Note 9
*Comment: Evening primrose oil may be helpful in improving diabetic neuropathy, but limited by small sample sizes and further validation by more studies
Are there any side effects of evening primrose oil?
Moderate supplementation with evening primrose oil is safe for most people in good health, and possible side effects or adverse effects that have been reported include: stomach upset, nausea, diarrhea, soft stools, and headaches (especially when used in large doses).
Safety precautions (10 contraindications to use)
1. Do not use by pregnant and lactating women (due to unknown safety)
2. Do not use for coagulation dysfunction and two weeks before surgery, which may increase the risk of bruising and bleeding (because hypolinolenic acid/gamma-linolenic acid in evening primrose oil has the effect of slowing down the speed of clotting)
3. Do not use in patients with epilepsy or schizophrenia, which may increase the risk of seizures
4. May cause allergic reactions, related symptoms are: rash, difficulty breathing, swelling of the face, lips, tongue or throat, if the above conditions occur after taking the above conditions, please seek medical attention immediately
5. Do not use in combination with anticoagulants, may increase the risk of bruising and bleeding, related drugs are: Aspirin, clopidogrel, diclofenac, ibuprofen, naproxen, dalteparin (dalteparin sodium), enoxaparin, heparin, Warfarin
6. Do not use in combination with Phenothiazine drugs (psychiatric drugs, with sedative and sleep aids), may cause epilepsy, related drugs are: chlorpromazine, fluphenazine (hydroxyflupromazine), trifluoperazine, thioridazine (methylthioridazine)
7. Do not use with herbs or health ingredients that may affect blood clotting function, which may increase the risk of bruising and bleeding, related ingredients include: angelica, chili, cloves, danshen, garlic, ginger, ginkgo, horse chestnut, ginseng, aspen, safflower alfalfa, saw palmetto, turmeric, willow.
8. A case report has stated that long-term use of evening primrose oil (more than one year) may increase the risk of inflammation, thrombosis and immunosuppression
9. Case reports have pointed to cases of lipoid pneumonia with long-term oral evening primrose oil
10. Do not combine with anti-human immunodeficiency virus (i.e. HIV) drugs, such as Lopinavir and ritonavir, which may slow down the breakdown of such drugs in the body and increase the risk of side effects.