Hi GillGrant,
The active ingredient in Evening Primrose Oil is GLA (Gamma Linolenic Acid). A better alternative is Starflower (Borage) Oil, which contains about 3 times the amount/concentration of GLA, drop for drop.
I was advised to take Starflower by a Breast Consultant as an anti inflammatory for hormonal breast pain. You need to take it every single day.
Love AgathaC