Riboflavin is widely distributed throughout all plant and animal cells. Good sources are dairy products, offal and leafy vegetables. Riboflavin is not destroyed appreciably by cooking, but is destroyed by sunlight. Riboflavin is a flavoprotein that is a cofactor for many oxidative reactions in the cell.

There is no definite deficiency, although many communities have low dietary intakes. Studies in volunteers taking a low riboflavin diet have produced:

angular stomatitis or cheilosis (fissuring at the corners of the mouth)

a red, inflamed tongue

seborrhoeic dermatitis, particularly involving the face (around the nose) and the scrotum or vulva.

Conjunctivitis with vascularization of the cornea and opacity of the lens has also been described. It is probable, however, that many of the above features are due to multiple deficiencies rather than the riboflavin itself.

Riboflavin 5 mg daily can be tried for the above conditions, usually given as the vitamin B complex.