Primrose has been used in traditional medicine as a remedy for muscular cramps and headaches. It was mentioned by Pliny as a remedy for rheumatism.
The whole plant is sedative and the tincture of the fresh plant in bloom has been used with success in extreme sensitiveness, restlessness and insomnia.
Primroses were considered fairy flowers in Ireland and Wales; they are held sacred by druids. Eating primroses is supposed to enable you to see fairies :-).