The following is taken from the ASPCA Animal Poison Control website.
The active ingredient in glow sticks, dibutyl phthalate, is not very toxic. It can cause some alarming signs such as drooling, hyperactivity, agitation and possibly aggressive behavior. Generally, the signs are caused by the bad taste of the liquid and last only a few minutes after biting into the stick.
Treatment is aimed at diluting the taste by offering water, a small amount of milk, tuna water, chicken broth, canned food, etc. Liquid on the skin or fur can be washed off with soap or shampoo and water. This helps avoid further glow fluid from being eaten when the cat licks itself.
Let me know if you have follow up questions.