Psyllium seed husk are indigestible and are a source of soluble dietary fiber. They are used to relieve constipation, irritable bowel syndrome, and diarrhea. They are also used as a regular dietary supplement to improve and maintain regular GI transit.syllium seed husk are indigestible and are a source of soluble dietary fiber. They are used to relieve constipation, irritable bowel syndrome, and diarrhea. They are also used as a regular dietary supplement to improve and maintain regular GI transit.