Tear Gas and Pepper Spray

The eye is an organ that has direct contact with the external environment. It can be injured in many ways, including by chemicals. 

Eyeball Structure

The center part of the front of the eyeball is clear and it lets in light into the eye like the lens of a camera. This part is called cornea and it overlies the colored part of the eye (iris). The rest of the eyeball coating is white (sclera) and has a thin layer of semi-transparent ‘skin’ on the front surface (conjunctiva). The conjunctiva also lines the inside of the eyelids. 

Chemical irritants

The ocular surface can be injured by strong chemicals, for example acids (e.g. vinegar), alkalis (e.g. detergent) and irritants (e.g. chili).

Pepper spray contains “oleoresin capsicum” which causes irritation of cornea, sclera and conjunctiva. It can cause pain, tearing and blepharospasm. Although the effect usually wears off after 1.5-2 hours of decontamination, residual corneal epithelial defect / scarring can occur and affect vision1

Tear gas often contains “chlorobenzalmalonitrile”, which reacts with moisture on the mucous membrane of the eye, hydrolyzes to acidic products and causes immediate irritation of ocular surface and thus copious tearing2

The severity of ocular injury caused by tear gas and pepper spray may be related to chemical agents themselves, total exposure dose, deployment technique and the way they are used in different settings3,4.

First aids in exposure to chemical irritants

  1. Get away from gas-filled areas to decrease exposure to irritants.
  2. Contaminated contact lens and clothing should be removed, followed by copious irrigation with water/ saline/ Diphoterine solution (first aid irrigating solution) for 10-20 minutes.
  3. If symptoms persist, please seek medical advice.


  1. Yeung MF, Tang WY. Clinicopathological effects of pepper (oleoresin capsicum) spray. Hong Kong Med J. 2015.;21(6):542-52
  2. M Brvar. Chlorobenzylidene malononitrile tear gas exposure: Rinsing with amphoteric, hypertonic, and chelating solution. Human & Experimental Toxicology. March 2015
  3. Haar et al. BMC Public Health (2017) 17:831. Health impacts of chemical irritant used for crowd control: a systematic review of the injuries and deaths caused by tear gas and pepper spray
  4. Kim YJ, Payal AR, Daly MK. Effects of tear gases on the eye. Surv Ophthalmol. 2016:61(4):434-42.

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