What Is Evening Primrose Oil?

A supplement commonly recommended for conditions that cause pain

Primrose oil softgels

Verywell / Anastasia Tretiak

Evening primrose oil is extracted from the seeds of evening primrose (Oenothera biennis), a plant native to North America. It gets its name from its yellow blossoms, which bloom in the evening.

The oil contains gamma-linolenic acid (GLA) and other omega-6 fatty acids that have both anti-inflammatory and pain-relieving, or analgesic, properties.

This article explores the available research on evening primrose oil, what it's commonly taken for, and potential side effects. You'll also learn about common dosages and how to store it safely.

What Is Evening Primrose Oil Used For?

Evening primrose oil is not an essential oil commonly used for aromatherapy. Rather, it is one that can be taken by mouth.

Alternative healthcare providers believe that evening primrose oil can aid in the treatment of numerous health conditions, including skin conditions and nerve and joint pain.

It's also sometimes taken for premenstrual syndrome (PMS), or symptoms leading up to menstrual periods, or the transition to menopause, or the end of menstruation.

Many of these potential benefits are attributed to GLA, a fatty acid found in soybeans, walnuts, seeds, and vegetable oils like rapeseed, canola, and linseed oils.

Some of the claims are supported by studies, but research is limited overall.

Menstrual Conditions

Evening primrose oil is commonly recommended for cyclical breast pain, which is linked to the menstrual cycle and occurs about a week before your period.

Research on this use is mixed, but seven of 10 clinical studies included in a 2019 research review suggested that evening primrose oil was helpful for breast pain.

For example, one study found that women who took 2 grams (g) of evening primrose oil or 2 g evening primrose oil plus 400 IU vitamin E daily for six months had slight improvements in the severity of their breast pain compared to those taking a placebo, or a sham treatment.

Evening primrose oil is also sometimes used for other symptoms of PMS or to alleviate menstrual cramps. However, to date, there is no conclusive evidence to support these claims.

Menopause

Evening primrose oil has long been used to treat hot flashes during the transition 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.

While the body of evidence is mixed, a 2013 study published in the Archives of Gynecology and Obstetrics found that a daily, 500-milligram (mg) dose of evening primrose oil provided modest relief of hot flashes after six weeks.

Although the severity of hot flashes improved when compared to those given a placebo, the duration and frequency of the episodes did not.

Skin Conditions

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

In the 1980s, evening primrose oil was heavily touted as an effective treatment for eczema by Canadian entrepreneur David Horrobin.

Despite a positive response from consumers, many of the claims have since been debunked by research.

According to a 2013 review of studies from the University of Minnesota Medical School, evening primrose oil proved no more effective in treating eczema than a placebo in each of the seven reviewed trials.

Many of the same conclusions have been drawn when investigating the effectiveness of evening primrose oil in treating psoriasis, a condition that causes scaly and itchy patches of skin, or acne, a condition in which pores get clogged with oil and dead skin cells.

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a type of autoimmune disease, meaning one in which the immune system attacks its own cells and tissues. With RA, the body primarily attacks its own joints.

Some studies have suggested that GLA can reduce pain and improve function in people with mild to moderate rheumatoid arthritis. Most of the results to date have been modest at best, however.

A 2011 review of studies from Australia concluded that GLA found in evening primrose, borage seed, or blackcurrant seed oil provided moderate relief of pain and disability in people with rheumatoid arthritis.

The most promising results were seen in people who used nonsteroidal anti-inflammatory drugs (NSAIDs) at the same time, triggering a slight improvement in morning stiffness and joint movement.

Diabetic Neuropathy

In 1993, evening primrose oil was first proposed as a possible treatment of diabetic neuropathy, an often debilitating type of nerve pain that mainly affects the feet and legs. Since then, there has been minimal evidence to support these claims.

A 12-month study from India involving 80 people with severe diabetic neuropathy looked into the treatment. It concluded that a daily 500- to 1,000-mg dose of evening primrose oil combined with 400 mg of vitamin E achieved pain relief in 88% of the participants.

However promising, the conclusions were limited by the lack of a control (placebo) group to make a fair comparison. Still, the findings were significant enough to warrant further research.

Osteoporosis

An increased intake of unsaturated fat is associated with a reduced risk of osteoporosis, which is bone mineral loss that causes bones to become weak and brittle. This condition especially affect women after menopause.

Primrose oil is made up almost entirely of unsaturated fat and is believed by some to counter the bone loss seen in women with osteoporosis.

An 18-month study from South Africa reported that the combined use of primrose oil, fish oil, and calcium supplements either slowed or reversed bone loss in older women (average age 79) compared to a control group of similar-age women given a placebo.

According to the research, women given the treatment combination experienced an increase of femoral (thigh) bone density of 1.3% (versus a loss of 2.3% in the placebo group).

While the bone density of the lumbar spine, or lower back, remained unchanged in primrose oil group, the placebo group experienced a 3.2% decrease in bone density.

Recap

There is some very limited evidence that supports the use of evening primrose oil for PMS-related breast pain, menopause-related hot flashes, joint pain in those with rheumatoid arthritis, nerve pain in those with diabetic neuropathy, or osteoporosis. However, more research is needed.

Possible Side Effects

Like most supplements, there hasn't been much research assessing the long-term safety of evening primrose oil.

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

  • Stomach upset
  • Headache
  • Nausea
  • Diarrhea

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

Precautions and Drug Interactions


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

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

  • Evening primrose oil may increase the risk of bleeding in people with bleeding disorders.
  • If you have upcoming surgery, you should stop taking evening primrose oil about two weeks beforehand to prevent excessive bleeding.
  • Pregnant women should not take evening primrose oil, since it may increase the risk of miscarriage or induced labor.

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

Recap

Evening primrose oil can interact with some medications, such as blood thinners and NSAIDs. It can also be dangerous for those with certain medical conditions, such as bleeding disorders. Always consult your healthcare provider before taking it.

Primrose oil soft gels
Verywell / Anastasia Tretiak 

Dosage and Preparation

Supplements are not regulated by the U.S. Food and Drug Administration (FDA) in the same way drugs are. As such, there are no universal guidelines regarding the appropriate use of evening primrose oil.

Generally speaking, a daily dose of 500 mg is considered safe in adults, although many can tolerate up to 1,300 mg a day without any side effects.

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

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 is more difficult to accurately dose.

Storage

Evening primrose oil contains a high proportion 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.

How Long Evening Primrose Oil Lasts

To extend the shelf life of the oil, keep it in its original container (which is typically blue to prevent sun exposure) and store it in the refrigerator.

Although primrose oil can keep for up to six months if stored this way, try to buy only as much as you can use within three months. The concentration of seed oil content tends to drop after three to four months because of oxidative deterioration—even with refrigeration.

How to Tell If Evening Primrose Oil Has Gone Bad

Because primrose oil only has a faint scent, it can often be difficult to tell if it has gone bad. It may darken or smell funny, but not always.

As such, you should always play it safe and discard any supplement after its use-by date.

Recap

Evening primrose oil usually comes in gelcap form. There is no standard dosage, but about 500 mg to 1,300 a day may be taken. To avoid a drop in quality, only buy about a three-month supply at a time and store it in the fridge.

What to Look For

Dietary supplements like evening primrose oil are not required to undergo the rigorous testing that pharmaceutical drugs do.

Instead, the FDA imposes certain standards regarding the manufacturing and labeling of these supplements.

Even so, there is often considerable variation in the quality of supplements like evening primrose oil.

To ensure quality and safety, only buy supplements certified by an independent body, such as the U.S. Pharmacopeia (USP), NSF International, or ConsumerLab.

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

There's some research that supports the use of evening primrose oil for certain conditions that cause pain. But since the studies are limited and often mixed, no firm conclusions about benefits can be made.

If you are interested in trying evening primrose oil, always discuss it with your healthcare provider and mention any medications you are taking and conditions that you have so that interactions and side effects can be avoided.

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13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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