Editor,—In 1996, CS incapacitant spray was sanctioned for the use of police forces in England and Wales. As its use increases the demands on accident and emergency departments from individuals who have been exposed to this will also increase. Some of the points in Worthington and Nee's review¹ are worth clarifying.

The experimental work into the safety of CS was performed on pyrotechnically generated CS.^{2, 3} The spray used by the police produces a mist that contains CS as a supersaturated solution or as a fine powder. The solution in the spray is a 5% w/v solution dissolved in methyl isobutyl ketone (MIBK). The American forces use a 1% solution.

Pulmonary oedema after CS exposure has been reported,² but only in conditions where the victim has been unable to escape, and is trapped in a confined area—that is, on exposure to very high concentrations. Equally burns to skin occur in specific conditions: high temperature, humidity, high concentrations, and prolonged exposure.

As mentioned at the outset these experiments were conducted on CS produced by a different method and it is difficult to extrapolate the results to a totally different type of exposure. The solvent, MIBK, has a low volatility, therefore in areas protected from air currents (behind ears, in skinfolds, under clothing bands, etc) it may not evaporate, prolonging the contact in warm moist areas. MIBK, itself, also has the potential to cause inflammation, dermatitis, and burns to the skin.

Although the standard advice regarding management of CS exposure is to remove the subject from the source and allow a flow of fresh air over the affected parts, if symptoms are persistant irrigation and bathing are required, as skin irritation may not be caused by CS but by MIBK.