Triggers of Cyclic Vomiting Syndrome

Most people can identify a specific condition or event that triggered an episode. The most common trigger is an infection. Another, often found in children, is emotional stress or excitement, often from a birthday or vacation, for example. Colds, allergies, sinus problems, and the flu can also set off episodes in some people.

Other reported triggers include eating certain foods (such as chocolate or cheese), eating too much, or eating just before going to bed. Hot weather, physical exhaustion, menstruation, and motion sickness can also trigger episodes.

source: http://digestive.niddk.nih.gov/ddiseases/pubs/cvs/index.htm