In 1977, there was an outbreak of photosensitivity dermatitis by among persons who had ingested a certain brand of chlorella tablets. At least 23 patients were identified in and around the Tokyo metropolitan area.
The unconsumed chlorella tablets collected from these patients invariably induced photosensitivity dermatitis in mice. These chlorella tablets contained large amounts of pheophorbide and its ester, which are well-known phototoxic pigments derived from chlorophyll, while chlorella tablets from another maker, which contained less than a tenth as much pheophorbide induced no photosensitivity lesion in mice.
Furthermore, a linear dose response relationship was observed between the severity of photosensitivity dermatitis in experimental animals and the content of pheophorbide in chlorella administered. However, the reaction induced by pheophorbide extracted from the suspect chlorella was weaker than that induced by the original chlorella sample.
It was confimed that ethanol, used in forming granules of chlorella before pelleting, activates chlorophyllase, which in turn hydrolyzes chlorophyll naturally contained in chlorella into pheophorbide and its ester.
We concluded that the photosensitivity dermatitis was caused by the chlorella tablets, which had been treated with ethanol. We believe that pheophorbide and its ester found in large amount in these tablets, have played a major role in inducing the photosensitivity dermatitis.
