Oenothera biennis

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Latest Edit: Hector 2014-03-18 (EDT)

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See Also Botanical Monographs

Evening Primrose (Oenothera biennis) is used to treat a range of conditions including digestive, immune and women's health concerns. To explore the characteristics, medicinal uses and prescribing considerations of this herb in more detail, check out the references indicated.[1], [2]


  • Common Names: Evening primrose, King's cure all, Tree primrose, Sundrop
  • Family: Onagraceae
  • Habitat: Oenothera biennis is native to North America and is now found in many temperate climates. It thrives in open areas, especially dunes and sandy soil.
  • Parts Used: Leaves, stem, bark, flowers, see (Evening primrose oil or EPO)
  • Constituents: Fixed oil containing gamma-linolenic acid (GLA) and linoleic acid
  • Medicinal Actions:
Herb: astringent, sedative, phytoestrogen
Oil:Hypotensive (via GLA, a prostaglandin E1 precursor), see Cardiac Tonic. Decreases PMS (tension and bloating), anti-inflammatory, nutritive, antiallergic,


Historical Uses:

Oenothera biennis was historically used by North American Native people for bruises, wounds, and asthma. It was used in Europe for gastrointestinal complaints, neuralgia, and whooping cough.

Medicinal Uses:


  • Other Conditions


  • PMS, mastalgia, and endometriosis
  • pro-thromotic states, hypertension, intermittent claudication
  • Other Conditions

Prescribing Considerations

The information provided is intended to augment the treatment from a naturopathic doctor or other trained medical professional. Although most herbs are generally safe, it is recommended that you avoid self-prescribing especially when there is an underlying ongoing medical condition, if you are on any prescription medications or if you are pregnant or breastfeeding.

Formulations and Preparation

  • Adult - 2-8g of seed oil daily in divided doses with food
  • Children - 2-6g of seed oil daily in divided doses with food

Best administered with a preservative such as vitamin E, and protected from oxidation


The safety and prescribing considerations for this herb include:[3], [4]

  • Generally regarded as safe.
  • Side-effects are rare and limited to headache, nausea, and diarrhea. May also cause inhibition of testosterone conversion to dihydrotestosterone.
  • Cautions and Contraindications
  • epilepsy and mania (speculative)
  • Drug-Herb Interactions.[2]
  • Tamoxifen - faster response to the drug in patients with estrogen-dependent breast cancer (human study)
  • Anticoagulants - may be potentiated (speculative)
  • Phenothiazines - when given for schizophrenia, seizures were reported (human study; however, in other case reports patients diagnosed with schizophrenia and treated with phenothiazines were later rediagnosed with having epilepsy)
  • Antiepileptics - may be less effective due to increased risk for seizure (speculative)
  • Colchicine - synergistic in multiple sclerosis for improvement of disability score (human study)
  • NSAIDs - reduced pain from NSAID-induced gastrointestinal lesions (human study)


  1. Boon Heather, Smith Michael (2009) 55 Most Common Medicinal Herbs: The Complete Natural Medicine Guide Second Edition Institute of Naturopathic Education and Research, CCNM Toronto.
  2. 2.0 2.1 Godfrey Anthony, Saunders Paul, Barlow Kerry, Gowan Matt (2011) Principles and Practices of Naturopathic Botanical Medicine, Advanced Botanical Medicine. V3 CCNM Press, Toronto.
  3. Stargrove Mitchell Bebell, Treasure Jonathan, McKee Dwight L (2008) Herb, Nutrient and Drug Interactions: Clinical Implications and Therapeutic Strategies.
  4. Brinker Francis (1997) Herbal Contraindications and Drug Interactions: Plus Herbal Adjuncts With Medicines, 4th Edition Eclectic Medical Publications.