A minor or isolated reaction can become chronic with repeated exposure to an allergen, or when other cells involved in the immune system, the t cells, come into play.

Often, the psychological problem is not isolated, it is likely to be a chain reaction of a certain event.

Neither polymethylmethacrylate nor polymethylmethacrylate-grafted copolymer could be isolated by the reaction of polystyrene methylene lithium prepared in ether solution with methyl methacrylate.