Enables the transfer of a solute or solutes from one side of a membrane to the other according to the reaction: allantoin(out) + H+(out) = allantoin(in) + H+(in) by secondary active transport. [ https://www.worldcat.org/search?q=bn%3A0815340729 http://www.tcdb.org/tcdb/index.php?tc=2.A.39.3.1 ]