This site's own FAQ addresses this directly: a small number of users report mild, temporary nausea if taken on an empty stomach, and rare mild allergic sensitivity is also possible.
Naming specific, if uncommon, side effects directly in the FAQ — rather than a blanket "consult your doctor" statement alone — is worth crediting as a more transparent approach than many similar sites take.
Take the capsule with a meal to reduce the chance of nausea, per this site's own recommendation, and stop use and consult a doctor if you notice any sign of an allergic reaction.