Well it’s obviously not going to “neutralise” radiation. I have no specific knowledge about this (I’d imagine the actual formula is classified) but if I was going to guess.
Some kind of oxidising agent (probably a fairly straightforward bleach) at as high a concentration as they can get away with, I’d imagine that some skin irritation is going to be acceptable compared to VX poisoning. It’s also effective against biological agents.
Specific neutralising and binding agents to the extent that it’s possible with the bleach. If it has chelating agents for radioactive stuff you might expect them to be bound to larger particles (plastic beads?) in the goop to prevent the radioactive material washing away and to simplify later decontamination.
The Bleach is going to be the big one, it will react with most biologically active substances and I know that is (or at least was) indicated in civilian chemical warfare response guidelines.
Under normal emergency circumstances regular detergent and water would be used primarily on people, but you seem to be talking about a topical gel.
If it’s designed for use on none living objects I’d expect much stronger bleach.