A compound of the formula: ##STR1## wherein the free valency of the groups A-, R- and --X--Y-- is attached to any of 2-, 4- and 5- positions of the thiazol ring, A is a C.sub.1-6 alkyl group, an aryl group which is unsubstituted or substituted with at least one substituent selected from the group consisting of hydroxy C.sub.1-6 alkoxy, aryl-(C.sub.1-6)alkoxy, halo-(C.sub.1-6)alkyl, halogen, and nitro,or 5- or 6-membered heterocyclic group containing at least one hetero atom selected from oxygen, nitrogen and sulfur, or a condensed heterocyclic group consisting of a heterocycle as defined above and a benzene nucleus, these two heterocyclic groups being unsubstituted or substituted with at least one substituent selected from halogen,R is hydrogen or a C.sub.1-6 alkyl group,X is --CO--or --NH--, andY is --NH--or --CO--, with the proviso that(a) X and Y cannot be the same group, and(b) when X is --CO--and Y is --NH--, the group --X--Y--is attached to 2- or 5-position,or a pharmaceutically acceptable salt thereof are nobel and useful as antiallergic.