Benzethonium chloride is a disinfectant (quaternary ammonium compound, cationic detergent) contained mainly in cleansing agents but also in locally active medications (against sore throat, spermicides).

Cationic detergents are more toxic than other detergents. Toxicity of concentrated solutions (more than 5-10%) is based upon their caustic action and upon their systemic toxic effects. Symptoms after dermal application of a concentrated solution are irritation, dermatitis, and bullous lesions. Contamination of the eye may lead from mild discomfort to corneal lesions depending on the concentration. Oral application of concentrated solutions leads to caustic burns of the oral and esophageal mucosa, nausea, emesis, abdominal pain, diarrhea, pulmonary edema, hypotension, metabolic acidosis, and depression of the central nervous system (sleepiness to coma), seizures, and death. Ingestion of small amounts of a diluted solution (less then 0.1%) is not likely to cause acute effects.

Grapefruit seed extracts containing benzethonium chloride in concentrations of 7-11% represent a major health risk if larger amounts of a concentrated solution are ingested (i.e. by mouthful). Exposure of the skin or the eye may cause toxic symptoms. There are no symptoms to be expected if only a few drops diluted in water are ingested.

The Swiss Toxicological Information Centre discourages consumers from administration of these extracts unless it is known which of them are containing benzethonium chloride and what the concentrations are.