Allantoin
In plain terms
A gentle soothing and skin-softening agent, one of the oldest and most universally tolerated ingredients in skincare. It calms redness and helps shed rough surface cells without the sting of acids. The cosmetic kind is made synthetically and is free of the plant toxins people sometimes worry about.
What the evidence shows
Allantoin is a soothing, mildly keratolytic skin conditioner that loosens dead surface cells gently enough for baby and post-procedure skin, while calming redness and supporting the barrier. The FDA recognizes it as a skin protectant at 0.5 to 2%, and the CIR panel has cleared it as used in cosmetics, finding no sensitization, no phototoxicity, and no systemic absorption at typical levels. Allantoin occurs naturally in comfrey, but that is the source of a common worry worth settling: comfrey also contains pyrrolizidine alkaloids, which are toxic to the liver when swallowed. Cosmetic allantoin is almost always synthesized, which leaves those plant compounds out entirely, so topical allantoin is not the comfrey extract people read warnings about. True allergy to it is rare. The practical read is simple: a quietly useful soother that suits sensitive, reactive, and barrier-stressed skin, and pairs well with stronger actives to take the edge off.
On the label
Listed as allantoin. If you specifically want to avoid plant-derived comfrey compounds, that is not an issue here, since cosmetic allantoin is synthetic; only whole comfrey extract on a label would raise that question.