Yes, if swallowed, and this is the most important thing on the page. Santol is eaten by sucking the sweet pulp off large seeds, which makes accidental swallowing easy, and swallowed santol seeds have caused intestinal perforation, abscess and peritonitis in a documented series of cases, mostly reported from the Philippines. The seeds are hard, smooth and tapered, and they lodge rather than passing through. This is a mechanical injury rather than a toxin, so the rule is simple and absolute: never swallow them, and be careful giving santol to children.

The pulp is sweet and sour with a soft, fibrous, faintly cottony texture, which is where the English name cotton fruit comes from. Flavour comparisons usually reach for a sour apple or a mangosteen, though santol is more acidic than either. There are two broad types, yellow and red, with the red generally sweeter. In Thailand and the Philippines it is most often eaten fresh with a salt, sugar and chilli dip, or preserved as candy and pickles.

It is untested rather than safe. Every FODMAP column on the santol row is unrated, which means nobody has measured it, not that it came back low. That distinction matters because an empty column can read as reassuring. If you are in a strict elimination phase, treat santol as an unknown fruit, try a small amount on a quiet day, and note that the salt, sugar and chilli it is usually served with are variables of their own.