Cases of anaphylaxis (a severe and life threatening allergic reaction) have been reported with psyllium consumption, so people with a possible allergy to psyllium or other members of the Plantaginaceae family should be cautious.[1][2] For people working with psyllium regularly, there is a risk of acquired sensitivity (or allergic exacerbation) due to exposure or inhalation of powdered particles.[3][4][5][6][7][8][9] Allergic responses are possibly due to the non-husk portions of psyllium seed, so psyllium husk that has been completely separated from other seed components may not have the same risk of adverse effects.[10]
Generally, all fiber is pro-flatus, meaning it causes gas buildup in the digestive system because of slowed motility and bacterial fermentation. Excess gas in the intestines may result in unwanted bloating, stomach cramping, feelings of fullness, flatulence, and “pull my finger” jokes.[11][12][13][14] Psyllium fiber, however, appears to produce less gas relative to other fibers, possibly due to its limited fermentation.[15][16][17][18]
Psyllium may worsen constipation if fluid intake is inadequate, and in severe cases, this can even lead to bowel obstruction. Due to the risk of bowel obstruction in the absence of fluids, psyllium use is not recommended in anyone who may be incapacitated and/or unable to maintain adequate fluid intake.[19][20]