The light stick contains two chemicals and a suitable fluorescent dye (sensitizer, or fluorophor). The chemicals in the plastic tube are a mixture of the dye and a derivate of phenyl oxalate ester (also called Cyalume). The chemical inside the glass vial is concentrated (about 35%) hydrogen peroxide. By mixing the peroxide with the phenyl oxalate ester, a chemical reaction takes place; the ester is oxidized, yielding two molecules of phenol and one molecule of peroxyacid ester. The peroxyacid decomposes spontaneously to carbon dioxide, releasing energy that excites the dye, which then deexcites by releasing a photon. The wavelength of the photon depends on the structure of the dye; eg. 9,10-bis(phenylethynyl)anthracene gives green light, 9,10-diphenylanthracene yields blue light, 5,6,11,12-tetraphenylnaphthacene yields red light. Other colors can be made of combination of dyes, eg. purple requires three dyes.

Glow sticks are not toxic. They can however be mildly irritating to the skin.

http://en.wikipedia.org/wiki/Light_stick