What Is Evening Primrose Oil?

Evening primrose oil is extracted from the seeds of Oenothera biennis, a plant native to North America and South America. It gets its name from its yellow blossoms, which bloom in the evening. The oil contains linoleic acid, gamma-linolenic acid (GLA), and other omega-6 fatty acids.

Evening primrose oil has been studied to treat conditions related to inflammation, pain, and menopause. This article explores the available research on evening primrose oil, what it's commonly taken for, and its potential side effects. You'll also learn about common dosages and how to store products safely.

Even though it is commonly used as a natural medicine, current research does not support taking evening primrose oil as a treatment for any medical condition.

Uses of Evening Primrose Oil

Evening primrose oil has been studied to treat conditions related to menstruation and menopause. These conditions include cyclical breast pain, premenstrual syndrome (PMS), hot flashes, and osteoporosis.

It has also been studied to treat skin and inflammatory conditions. This section provides an overview of studies for these conditions.

The way evening primrose oil works is not completely understood yet. Scientists have suggested it has to do with chemical components in the oil extracted from the seeds. Many potential benefits are attributed to GLA, an omega-6 fatty acid.

The evidence for evening primrose oil as a treatment is supported by small, preliminary studies and reviews of those studies. Some of these studies were done in GLA itself rather than evening primrose oil. The research is limited, and conclusions about its effects can’t be drawn yet.

Cyclical Breast Pain

Evening primrose oil has been studied to treat cyclical breast pain linked to the menstrual cycle that occurs about a week before your period. Research results on this use are mixed.

Researchers reviewed 13 clinical studies that used evening primrose oil to treat mastalgia. It was compared with vitamin E, topical nonsteroidal anti-inflammatory drugs (NSAIDs), and danazol (a hormone). They concluded that evening primrose oil was not better or worse than the other treatments for mastalgia (breast pain).

Additionally, researchers reviewed five studies that compared evening primrose oil with a placebo (an ineffective substance), one study that compared it with bromocriptine and danazol, and one study that compared it with vitagnus. The placebo studies suggested participants who took evening primrose oil had less pain than those in the placebo groups. In the bromocriptine and danazol study, 55% of participants who took evening primrose oil reported decreased breast pain. In the vitagnus study, the average pain decreased in the evening primrose oil group but was not significantly different from the treatment group.

Premenstrual Syndrome (PMS)

Evening primrose oil has been studied to treat PMS, a common group of symptoms experienced around the menstrual cycle. Symptoms vary in severity and include abdominal cramps and mood changes.

Researchers extensively reviewed conditions related to menstruation and menopause, including PMS. The review highlighted eight studies comparing evening primrose oil with a placebo for PMS and one study comparing GLA with a placebo. One evening primrose oil study showed a significant decrease in PMS severity, and the GLA study showed a shortened duration and decreased severity of PMS.

Hot Flashes

Evening primrose oil has been studied to treat hot flashes during perimenopause, the transitional period to menopause. These sudden feelings of extreme warmth in the upper body are a form of flushing caused by hormonal changes that may be due to reduced levels of the hormone estradiol.

Researchers conducted a study on 80 people assigned female at birth who were postmenopausal to compare black cohosh and evening primrose oil to treat hot flashes. The severity of symptoms in both groups improved significantly after eight weeks, but black cohosh was more effective than evening primrose oil in reducing the number of hot flashes.

Scientists conducted another study in 170 people assigned female at birth that compared evening primrose oil with a placebo for hot flashes. Though there was no difference between groups in hot flashes, they found that night sweats reported in the treatment group were fewer and less severe.

Additionally, a six-week study was done with evening primrose oil vs. placebo for hot flashes in 56 people assigned female at birth who were menopausal. The researchers found improvements in the treatment group compared with the placebo in decreased severity of hot flash symptoms, improvement in social activities, and improvement in sexuality. Similar to the other studies, there was no decrease in the frequency of hot flashes.

The use of evening primrose oil looks promising for conditions related to menstruation and menopause, but the quality of the studies and results were mixed. Further research is needed. Studies about osteoporosis, which can be connected to menopause, are below.

Osteoporosis

The connection between unsaturated fat and reduced risk of osteoporosis is a topic of interest and continued study. Osteoporosis is a condition in which bone mineral loss causes bones to become weak and brittle. This condition primarily affects people assigned female at birth who've completed menopause.

Although omega-6 fatty acids are found in evening primrose oil, some studies report on the bone density effects of all polyunsaturated fatty acids. That includes omega-3 and others.

Researchers conducted a review of polyunsaturated fatty acids in bone mineral density. The review included an 18-month study of combined treatment with evening primrose oil, fish oil, and calcium supplements. Results showed slowed or reversed bone loss in older people assigned female at birth compared with a control group of older people assigned female at birth given a placebo.

In a genomic (genetics on a large scale) study, scientists reviewed genetic information from several thousand participants in a biobank. They investigated the connection between omega-6 fatty acids and bone mineral density. They found associations between fatty acids and bone mineral density but not omega-6 fatty acids. This is not a clinical study with an intervention but a promising avenue for future research.

Skin Conditions

Eczema, also known as atopic dermatitis, is a skin condition that causes scaly and inflamed skin.

As part of a review of borage oil and evening primrose oil for eczema, researchers reviewed 19 studies that compared evening primrose oil with a placebo. Evening primrose oil was not more effective for treating eczema than a placebo.

In clinical research, acne, a condition in which pores get clogged with oil and dead skin cells, has also been treated with evening primrose oil.

Scientists conducted a small, nine-month study with 50 participants that added evening primrose oil to isotretinoin, a standard acne treatment. Twenty-five were given isotretinoin alone, and 25 were given evening primrose oil and isotretinoin. Improvement in acne was observed in both groups, and the group that took evening primrose oil noticed additional skin hydration.

Evening primrose oil and various other sources of fatty acids continue to be studied in psoriasis, a condition that causes scaly and itchy patches of skin.

Researchers reviewed the effects of fatty acids, including evening primrose oil, on metabolic processes involved in psoriasis. They found that evening primrose oil, linoleic acid, and other fatty acids were beneficial for psoriasis, but the review did not provide specific clinical results.

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease, meaning the immune system attacks its cells and tissues. With RA, the body primarily attacks its joints. 

Researchers conducted a 12-week study with fish oil and evening primrose oil in 60 participants with active rheumatoid arthritis. One group took fish oil alone, and another took both evening primrose oil and fish oil. Researchers found improvements in disease activity score, number of tender joints, and decreased pain in both treatment groups.

Another review was done on studies that used GLA, borage seed oil, or black currant seed oil for rheumatoid arthritis. Results showed moderate relief of pain and disability in people with rheumatoid arthritis. The best outcomes were seen in people who simultaneously used nonsteroidal anti-inflammatory drugs (NSAIDs), which slightly improved morning stiffness and joint movement.

Multiple Sclerosis

Multiple sclerosis is an autoimmune disease that affects the coverings of nerves in the brain and spinal cord. It can be relapsing (gets better, then worse) or progressive (continues to worsen).

Scientists studied evening primrose oil vs. placebo for multiple sclerosis in 52 participants over three months. They found that the treatment group improved pain, fatigue, and cognitive function compared with the placebo.

This was a small study, so conclusions cannot be applied to a larger population yet.

Diabetic Neuropathy

Evening primrose oil has been studied to treat diabetic neuropathy, a condition of nerve dysfunction resulting from long-term diabetes.

Scientists conducted a 12-week study that used GLA, alpha lipoic acid, and a placebo in 73 participants with diabetic neuropathy. They found that both treatment groups decreased pain and total symptoms compared with the placebo. There was not a statistically significant difference between the two treatment groups.

Another 12-month study used vitamin E and evening primrose oil to treat 80 people with painful diabetic neuropathy. Researchers concluded that evening primrose oil combined with vitamin E improved pain in 88% of the participants.

However promising, the conclusions were limited by the small number of studies and the use of a combination treatment. The findings were enough to warrant further research but not to draw conclusions.

What Are the Side Effects of Evening Primrose Oil?

There hasn't been much research assessing the long-term safety of evening primrose oil. These side effects are documented in short-term studies.

Common Side Effects

In some cases, evening primrose oil may cause side effects such as:

• Stomach upset
• Bloating
• Headache
• Nausea
• Altered taste
• Diarrhea
• Seizure

Most of the side effects are low grade and resolve on their own once the treatment is stopped.

Severe Side Effects

Information about severe side effects is lacking. However, if you have signs of an allergic reaction, including but not limited to skin inflammation, hives, cramping, and diarrhea, please call 911 and seek immediate medical help.

Precautions

Evening primrose oil should be used cautiously if you have certain medical conditions. Among them:

• Evening primrose oil may increase the risk of bleeding. Use caution if you have a bleeding disorder.
• Any medicine or herb that inhibits clotting or increases the risk of bleeding should be stopped for at least two weeks before surgery. Ask your healthcare provider if any of your medications or supplements also need to be stopped temporarily if you have surgery planned.
• Although there is an ongoing study about evening primrose oil for the induction of labor in pregnancy, there is not enough evidence to make a recommendation. Caution is always advised in this population.
• Caution is also warranted in breastfeeding.

Let your healthcare provider know if you are taking evening primrose oil—or any supplement—to avoid drug interactions and potentially severe side effects.

Dosage: How Much Evening Primrose Oil Should I Take?

The FDA does not regulate supplements in the same way they regulate drugs. As such, there are no universal guidelines regarding the appropriate use of evening primrose oil.

Evening primrose oil is generally considered safe for use in adults. There is no recommended dosage of evening primrose oil. Doses in studies ranged from 240 milligrams daily to 4 grams daily.

Due to the lack of research, evening primrose should not be given to children or older adults without first consulting a healthcare provider.

Evening primrose oil is available in many health food stores and pharmacies. It is typically sold in gelcap form. Bottled primrose oil is also available, but it is more difficult to accurately dose.

Interactions

Evening primrose oil can interact with several medications, either reducing the drug's efficacy or triggering side effects. These include:

• Anticoagulants (blood thinners) like Jantoven (warfarin)
• NSAIDs like diclofenac, ibuprofen, and aspirin
• Antipsychotic drugs like chlorpromazine (a phenothiazine drug)
  
• Human immunodeficiency virus (HIV) medications, such as lopinavir

It is essential to carefully read a supplement's ingredient list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review the supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.

How to Store Evening Primrose Oil

Evening primrose oil contains a high amount of unsaturated fats, which are susceptible to a breakdown process called oxidative deterioration. If this occurs, the quality of the supplements is compromised. Any product rich in unsaturated oil can go rancid, including bottled primrose oil and primrose oil gel caps.

Storage instructions vary for different products. Carefully read the directions and packaging label on the container. Keep your medications tightly closed and out of the reach of children and pets, ideally locked in a cabinet or closet. Try to store your medications in a cool and dry place.

Discard after one year or as indicated on the packaging. Avoid pouring unused and expired products down the drain or in the toilet. Visit the FDA's website to know where and how to discard all unused and expired medications. You can also find disposal boxes in your area.

Ask your healthcare provider if you have any questions about the best ways to dispose of your medications or supplements.

If you plan to travel with evening primrose oil, get familiar with your final destination's regulations. Checking with the U.S. Embassy or Consulate might be a helpful resource.

Similar Supplements

Similar supplements include but aren't limited to:

• Black cohosh
• Black currant seed
• Borage oil
• Gamma-linolenic acid (GLA)
• Vitex
  

Like evening primrose, borage oil contains significant amounts of GLA.

Sources of Evening Primrose Oil & What to Look For

You can find evening primrose oil supplements in pharmacies, health food stores, and online.

Fatty acids such as GLA and linoleic acid are also present in some foods:

• Seeds
• Oils
• Nuts

Food Sources of Evening Primrose Oil

Evening primrose oil is not present in foods. It can only be found in the seeds of the Oenothera biennis plant.

Evening Primrose Oil Supplements

Evening primrose oil can be found as a capsule, gelcap, or oil.

If you are strictly vegan or vegetarian, only choose brands labeled "vegetarian-safe" or "vegetarian softgels." Unless this is stated clearly on the label, the capsule may be made with animal-based gelatin derived from cows or pigs.

Summary

Evening primrose oil comes from the seed of the evening primrose plant. It contains linoleic acid and GLA, which are omega-6 fatty acids.

Some research supports evening primrose oil for certain conditions that cause pain or inflammation. But since the studies are limited and often have mixed results, no firm conclusions about benefits can be drawn.

Evening primrose oil can be a dietary supplement in most pharmacies and health food stores. If you are interested in trying evening primrose oil, always discuss it with your healthcare provider. You should mention any medications you are taking and conditions you have, such as bleeding disorders, so that interactions and side effects can be avoided.