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Evening primrose oil has a long history as a natural health remedy. It’s been hailed as everything from a hair loss solution to a cure for acne. But what is it exactly?

Evening primrose (Oenothera biennis), sometimes called “the night willow herb,” is a flowering plant. It’s also a night owl, blooming at sunset instead of sunrise. The oil pressed from its seeds, aka evening primrose oil (EPO for short), is a gentle carrier oil.

It can be ingested, applied as a topical balm, or blended with other carrier oils in skin care formulations.

Devotees use it for all sorts of ailments:

The reason EPO just might work is that it’s full of gamma-linolenic acid (GLA), an omega-6 fatty acid that reduces inflammation.

Here are 13 science-supported benefits of adding EPO to your daily routine.

Natural health and fertility sites often recommend EPO to accelerate babymaking. The idea is that the GLA in the oil improves cervical mucus and egg quality just like other omega fatty acids do.

More research is needed, but if you’re trying to get pregnant, ask your doctor about EPO. Makes sense to add these healthy fats to your diet.

How to use it

Buy a quality EPO supplement and start with the smallest recommended dosage. And buyer beware — if you do get pregnant, stop taking EPO stat. The National Institutes of Health says it could “increase the risk of some complications of pregnancy.”

Hormone-related sweats and hot flashes are the worst, so we’re here for any science-backed remedies. EPO to the rescue!

A 2013 study found that menopausal women who took daily EPO supplements for 6 weeks reported fewer hot flashes — and the ones they did have were way less fiery. Even better? The women said cooling their hot flashes also improved lifestyle factors like social interactions and lovemaking.

How to use it

Stock up on enough EPO to take 500 milligrams twice a day for 6 weeks.

Deal with breakouts on the reg? EPO could be your new BFF. The GLA ingredient soothes inflammation while the oil itself adds a dewy glow.

In one promising study, 45 people with acne had fewer lesions after taking GLA.

Some research suggests EPO also soothes cheilitis, a swollen, red rash around your lips caused by isotretinoin (aka Accutane, a common anti-acne drug).

How to use it

To see the same benefits as research participants, stick with the regimen as long as they did. It’s a marathon, not a sprint!

In the cheilitis study, participants took six 450-milligram pills full of EPO three times a day for 8 weeks. In the GLA study, participants took two capsules containing 200 milligrams of GLA twice a day for 10 weeks.

The research is thin, but EPO fans say it soothes eczema.

In one practically retro study (1991), results indicated that the GLA in EPO nourishes the top layer of skin, which gets inflamed by eczema.

Unfortunately, a 2013 review of 27 studies concluded that popping EPO supplements isn’t any more effective than taking a placebo. So this benefit might be a draw.

How to use it

If you’re interested in giving EPO a whirl based on anecdotal evidence, you have a couple of options. You could take the recommended dose of an EPO supplement. You could also apply the oil directly to your eczema as a salve.

To use directly on your skin, apply about 1 milliliter of just 20 percent EPO no more than twice a day. It’s also a good idea to talk to your dermatologist first, since they’ll know if EPO is a safe match with your regular treatment.

Skin feeling a little “meh” these days? EPO’s healthy helping of GLA is known to improve elasticity, firmness, moisture — all the good stuff.

A 2005 study suggests taking EPO boosts your body’s stores of skin-nourishing GLA (a fatty acid your skin can’t produce on its own). A 2011 study affirmed this when participants with dry skin noticed an improvement after noshing on GLA-rich foods.

How to use it

Take 500 milligrams EPO capsules 2 to 3 times a day for up to 12 weeks. You could also snack on GLA-rich foods like hemp seeds, oats, and spirulina.

Research on rats instead of humans should be taken with a grain of salt, but here’s the tea: In a 2014 study, rats that dosed on EPO experienced reduced blood cholesterol and lower levels of inflammation.

Since heart disease is often linked to inflammation, EPO could indirectly reduce your risk of heart disease. More research with humans is needed, but it’s something you could discuss with your doctor.

How to use it

If you’re worried about your heart health, check with your doc before dosing on EPO. In general, it’s best to start with the smallest recommended dose of a new-to-you supplement.

The jury’s still out on this one, but some studies indicate that EPO could lower blood pressure.

In one study, participants who took EPO had a slightly higher systolic blood pressure. Researchers said results were “intriguing,” but noted there were too many factors to prove a causal relationship.

Another review of studies revealed that evidence of EPO reducing high blood pressure is too limited to recommend it in a clinical setting. It is possible that EPO might interfere with medications.

How to use it

If your doctor gives you the green light, start with a standard EPO dose (about 500 milligrams) twice a day. Avoid other blood pressure meds or supplements when taking EPO.

There’s dated research that EPO could relieve PMS symptoms like irritability, moodiness, and even bloating. Again, it’s because of GLA, which triggers a chemical reaction that seems to prevent PMS.

A 2010 study further affirmed that supplements containing EPO (but also packed with vitamin B-6 and vitamin E) helped with PMS. Of course, we don’t know whether the EPO or other vitamins deserve the credit.

How to use it

You know the drill — start with the smallest dose possible and work up to relieve your symptoms. For PMS, that could be anywhere from 500–6,000 milligrams one to four times a day.

Your emotions might not be the only thing that gets a little sensitive when the crimson tide rolls. If your boobs get achy on the reg, EPO could help.

Research suggests the GLA in EPO reduces inflammation, which causes your monthly boob pain. The same study includes daily doses of vitamin E, so it’s tough to say whether it was the combo or EPO alone that helped.

How to use it

Down 1–3 grams (or 2.4 milliliters) of EPO each day for 6 months. To boost your chances of success, also take 1,200 milligrams of vitamin E daily.

You already know the GLA in EPO is anti-inflammatory, which means it has the potential to soothe all kinds of aches — boob pain, joint pain, and so on.

A review of the research further backed up claims that a dose of EPO a day keeps arthritis away. Bonus — it didn’t seem to cause any side effects!

How to use it

Take a cue from the research and take 560–6,000 milligrams of EPO a day for at least 3 months (and up to a year).

Health conditions like diabetes often come with an unhelpful side of nerve pain, tingling, weakness, and sensitivity to extreme temps. The good news is that GLA soothes damaged nerve symptoms.

In a 2014 study of 70 people with diabetes, participants who took EPO and vitamin E for a year experienced a reduction in nerve pain.

How to use it

Take 400 milligrams of vitamin E and 500–1000 milligrams of EPO a day for up to a year.

Whether you’re losing hair by the handful or are looking to give your locks a little extra “oomph,” EPO could help.

Research is still limited, but the arachidonic acid in EPO has been known to boost your hair growth potential. And again, GLA’s anti-inflammatory powers could help make your scalp a happier, healthier environment for your hair.

How to use it

Using EPO to help your hair could mean taking the standard 500-milligram dose a day. Or you could try a topical treatment, using EPO as a mask on your scalp and hair or mixing a few drops of EPO into your daily shampoo.

You’ll find EPO in heaps of weight loss supplements, but what does science say? Not much, TBH.

As you know by now, EPO contains GLA, which is an omega-3 fatty acid. Research suggests balancing your omega-3 and omega-6 intake reduces your risk of obesity. So yeah, in a way, keeping those fatty acids balanced is part of maintaining a healthy weight.

But claims beyond that just don’t hold weight (pun intended!). Even older studies suggest EPO doesn’t make a difference in weight loss efforts.

There’s been enough research on EPO to consider it generally safe for short-term use. But remember — supplements are a pretty unregulated industry. They don’t fall under FDA monitoring, so there could be issues with quality and dosing suggestions.

Take these precautions to lower your risks:

  • Purchase any EPO from reliable, well-researched companies.
  • Check to make sure your product has a certificate of analysis (COA) for the batch you’re buying, which guarantees you’re getting what you paid for (no toxic fillers, for instance).
  • Beware sellers mislabeling EPO as an essential oil — it’s a carrier oil.
  • Start with the lowest dose to help prevent side effects.
  • Avoid EPO while pregnant.
  • Avoid EPO if you’re on blood pressure meds.
  • Check with your doctor before you start any supplement or herb.

As for side effects, every rose has its thorn, right? Here are the most common:

  • headache
  • soft or sludgy poop
  • upset stomach or stomach pains

If you’re allergic to other flowering plants or oils, be cautious about ingesting EPO. Watch for these signs of an allergic reaction:

  • swelling or redness in your hands or feet
  • rash
  • trouble breathing
  • whistling cough or other wheezing sounds

Evening primrose oil (EPO) has been used as a remedy for inflammation and several other skin and health conditions for years. More research is necessary to recommend it as a clinical treatment.

EPO combined with vitamin E could alleviate symptoms, but it shouldn’t replace meds recommended by your doctor.

Always use the lowest dose possible to reduce your risk of side effects. Talk to your doctor about the EPO method and dosage best for your conditions.