Evening primrose oil is ineffective for eczema: a fascinating tale of mischief

One of the best-selling supplements in the UK as well as several other countries is evening primrose oil (EPO). It is available via all sorts of outlets (even respectable pharmacies – or is that supposedly respectable?), and is being promoted for a wide range of conditions, including eczema. The NIH website is optimistic about its efficacy: “Evening primrose oil may have modest benefits for eczema.” Our brand-new Cochrane review was aimed at critically assessing the effects of oral EPO or borage oil (BO) on the symptoms of atopic eczema, and it casts considerable doubt on this somewhat uncritical view.

Here is what we did: We searched six databases as well as online trials registers and checked the bibliographies of included studies for further references to relevant trials. We corresponded with trial investigators and pharmaceutical companies to identify unpublished and ongoing trials. We also performed a separate search for adverse effects. All RCTs investigating oral intake of EPO or BO for eczema were included.

Two experts independently applied eligibility criteria, assessed risk of bias, and extracted data. We pooled dichotomous outcomes using risk ratios (RR), and continuous outcomes using the mean difference (MD). Where possible, we pooled study results using random-effects meta-analysis and tested statistical heterogeneity.

And here is what we found: 27 studies with a total of 1596 participants met our inclusion criteria: 19 studies tested EPO, and 8 studies assessed BO. A meta-analysis of results from 7 studies showed that EPO failed to improve global eczema symptoms as reported by participants and doctors. Treatment with BO also failed to improve global eczema symptoms. 67% of the studies had a low risk of bias for random sequence generation; 44%, for allocation concealment; 59%, for blinding; and 37%, for other biases.

Our conclusions were clear: Oral borage oil and evening primrose oil lack effect on eczema; improvement was similar to respective placebos used in trials. Oral BO and EPO are not effective treatments for eczema.

The very wide-spread notion that EPO is effective for eczema and a range of other conditions was originally promoted by the researcher turned entrepreneur, D F Horrobin, who claimed that several human diseases, including eczema, were due to a lack of fatty acid precursors and could thus be effectively treated with EPO. In the 1980s, Horrobin began to sell EPO supplements without having conclusively demonstrated their safety and efficacy; this led to confiscations and felony indictments in the US. As chief executive of Scotia Pharmaceuticals, Horrobin obtained licences for several EPO-preparations which later were withdrawn for lack of efficacy. Charges of mismanagement and fraud led to Horrobin being ousted as CEO by the board of the company. Later, Horrobin published a positive meta-analysis of EPO for eczema where he excluded the negative results of the largest published trial, but included results of 7 of his own unpublished studies. When scientists asked to examine the data, Horrobin’s legal team convinced the journal to refuse the request.

The evidence for EPO is negative not just for eczema. To the best of my knowledge, there is not a single disease or symptom for which it demonstrably works. Our own review of the data concluded ” EPO has not been established as an effective treatment for any condition”

Our new Cochrane review might help to put this long saga to rest. In my view, it is a fascinating tale of a scientist being blinded by creed and ambition. The results of such errors can be dramatic. Horrobin misled all of us: patients, health care professionals, scientists, regulators, decision makers, businessmen. This caused unnecessary expense and set back research efforts in a multitude of areas. I find the tale also fascinating from other perspectives; for instance, it begs the question why so many ‘respectable’ manufacturers and retailers are still allowed to make money on EPO. Is it not time to debunk the EPO-myth and say it as clearly as possible: EPO helps only those who financially profit from misleading the public?