Histamine and ascorbic acid in human blood.

Analysis of 437 human blood samples has shown that when the plasma-reduced ascorbic acid level falls below 1 mg/100 ml, the whole blood histamine level increases exponentially as the ascorbic acid level decreases. When the ascorbic acid level falls below 0.7 mg/100 ml, there is a highly significant increase in the blood histamine level. Oral administration of ascorbic acid (1 g daily for 3 days) to 11 selected volunteers resulted in a reduction of the blood histamine level in every instance.