There are a few similar species of Psyllium existing around the world. Plantago psyllium, Plantago indica, and Plantago ovata Forsk. Are the most frequently used. These annual plants are native to the Mediterranean region and the seeds and seed husks are used medicinally. Psyllium seed has laxative properties due to the swelling of its husk in water. This forms a viscous solution that keeps the feces full of water and soft. This bulking activity promotes the movement of the feces. Psyllium has been shown to bind to bile acids, an activity that can lower fat intake and serum cholesterol concentration. Psyllium is one of the most popular additions to bulking laxatives, and is often added to a cholesterol-reducing diet.

Uses would include chronic constipation, stool softening (hemorrhoids, post-rectal surgery), irritable bowel syndrome, and to increase dietary fiber. There have been some cases of allergic responses to psyllium, although these seem to be rare. As with other water-retaining fibers, a choking hazard does exist if improper mixing or inadequate liquid intake allows the psyllium powder to remain in the throat as it begins to swell. General caution usually prevents this from happening. Psyllium is most often sold in bulk, although various solid bars have also become available.