Many different products have historically been used as moth repellents. In the United States, paradichlorobenzene has largely replaced both camphor and naphthalene as the most common active component of moth repellent and moth flakes because of its decreased toxicity. However, because paradichlorobenzene is widely available and because life-threatening camphor and naphthalene toxicity still occur, all of these xenobiotics need to be considered in evaluating possible exposure moth repellent.
Camphor (2-bormanone, 2-camphonone), a cyclic ketone of the terpene group, is an essential oil distilled from the bark of the camphor tree, Cinnamomum camphora. Today, most camphor is synthesized from the hydrocarbon pinene, a derivative of turpentine oil. Camphor has been used as an aphrodisiac, contraceptive, abortifacient, suppressor of lactation, analeptic, cardiac stimulant, antiseptic, cold remedy, muscle liniment, and drug of abuse.27,34,40,45,50,60,71,72
Camphorated oil and camphorated spirits contain varying concentrations of camphor. Historically, most camphorated oil was 20% weight (of solute) per weight (of solvent) (w/w) camphor with cottonseed oil, and most camphorated spirits contained 10% w/w camphor with isopropyl alcohol. Toxicity and death following ingestion of camphorated oil, which was confused with castor oil and cod liver oil, prompted the FDA to ban the nonprescription sale of camphorated oil in the United States in 1983.3,21,40,64,81 Today, based on the 1983 FDA ruling, nonprescription camphor-containing products may not have greater than an 11% concentration of camphor. Camphorated oil is still used as an herbal remedy and muscle liniment, and products containing greater than 11% camphor can still be purchased outside of the United States.78
Common camphor-containing products include cold sore ointments (usually <1% camphor), muscle liniments, rubefacients (usually 4%–7% camphor), and camphor spirits (usually 10% camphor). Paregoric, camphorated tincture of opium, contains a combination of anhydrous morphine (0.4 mg/mL), alcohol (46%), and benzoic acid (4 mg/mL) but only a small amount of camphor.43 Camphor for industrial use can be purchased legally in the United States and contains up to 100% camphor. Occupational exposures to camphor occur during the manufacture of plastic, celluloid, lacquer, varnish, explosives, embalming fluids, and numerous pharmaceuticals and cosmetics.35
Although products containing lower concentrations of camphor are implicitly safer, life-threatening toxicity and death may still result, usually from misuse or intentional overdose. Most reported cases of acute camphor poisoning are unintentional ingestions of camphor-containing liquids mistaken for other medications.3,40,63,79 According to data obtained by the American Association of Poison Control Centers (AAPCC), each year there are approximately 10,000 exposures to camphor with very few reports of "major" toxicity. Over the past 20 years, according to the AAPCC, only six reported deaths were attributable to camphor, all in adults, at least two of which occurred in the setting of an intentional suicidal overdose. Chapter 135 contains complete references and discussion of the AAPCC data.