Glow sticks contain hydrogen peroxide, and phenol is produced as a by-product. It is advisable, therefore, to keep the mixture away from skin and to prevent accidental ingestion if the glow stick case splits or breaks. If spilled on skin the chemicals could cause slight skin irritation, swelling, or, in extreme circumstances, vomiting and nausea. Some ravers will cut or break open a glow stick and apply the glowing solution directly to bare skin in order to make their bodies glow. Some of the chemicals used in older glow sticks were thought to potentially be carcinogens. The sensitizers used are polynuclear aromatic hydrocarbons, a class of compounds known for their carcinogenity. Also it is wise to avoid all contact with thin membranes such as the eye or nasal area. Despite reports to the contrary[which?], it is not safe to smoke or ingest glowing phenol, and it will not produce any drug-like effects. The fluid contained in glow sticks can also dissolve some types of plastic.