Effects of incapacitant spray deployed in the restraint and arrest of detainees in the Metropolitan Police Service area, London, UK: a prospective study

Forensic Sci Med Pathol. 2014 Mar;10(1):62-8. doi: 10.1007/s12024-013-9494-7. Epub 2013 Nov 10.


Purpose: In the United Kingdom (UK) police restraint and control of detainees is undertaken by assorted means. Two types of incapacitant spray (IS) are approved by the UK Home Office for use: CS (o-chlorobenzylidine malononitrile, dissolved in an organic solvent--methyl iso-butyl ketone and pelargonic acid vanillyamide (PAVA). The aim of this study was to document the effects of incapacitant sprays, by symptom assessment and medical examination, within a few hours of deployment.

Methods: A detailed proforma was produced to explore the nature of the arrest, the nature of exposure to the incapacitant spray, the type of incapacitant spray, the symptoms experienced and the medical findings.

Results: 99 proformas were completed. 74 % were completed by detainees and 26 % were completed by police officers. 88 % were exposed to CS spray, the remainder to PAVA spray. The mean time of assessment after exposure was 2.8 ± 2.33 h (mean ± SD). The most frequent sites of IS contact were the face and scalp (n = 78), and exposure to the left and right eyes (n = 32). The most common symptoms were: painful eyes (n = 68); red eyes (n = 58); runny nose (n = 59); lacrimation (n = 55); nasal discomfort (n = 52); skin irritation (n = 49); and skin burning (n = 45). The most common medical findings were: conjunctival erythema (n = 34); skin erythema (n = 21); and rhinorrhea (n = 20).

Conclusions: Symptoms and signs of exposure to IS lasted longer than was expected (a mean of 2.8 h). Approximately 30 % of those exposed had ocular effects and 20 % had skin effects. The findings of this study will enable the guidelines on the expected effects and duration of symptoms resulting from exposure to incapacitant sprays to be reviewed and suggestions for their management to be refined.

MeSH terms

  • Adolescent
  • Adult
  • Aerosols
  • Benzylamines / adverse effects*
  • Crime*
  • Eye / drug effects
  • Eye Diseases / chemically induced
  • Eye Diseases / diagnosis
  • Fatty Acids / adverse effects*
  • Female
  • Humans
  • Irritants / adverse effects*
  • Law Enforcement*
  • London
  • Male
  • Middle Aged
  • Police*
  • Prospective Studies
  • Restraint, Physical*
  • Skin / drug effects
  • Skin Diseases / chemically induced
  • Skin Diseases / diagnosis
  • Time Factors
  • Young Adult
  • o-Chlorobenzylidenemalonitrile / adverse effects*


  • Aerosols
  • Benzylamines
  • Fatty Acids
  • Irritants
  • pelargonic acid vanillylamide
  • o-Chlorobenzylidenemalonitrile