What is pepper spray?

All bear pepper sprays have in common the following 3 components: 1) oleoresin capsicum (OC for short; the oily residue extracted from hot red peppers that naturally contains the active ingredient - capsaicin - that elicits an intense burning sensation), 2) a carrier, or base, fluid into which the oleoresin capsicum is mixed to thin and dilute it, and 3) a propellant that supplies the energy to expel the carrier and active ingredients from the can.

What exactly is the “oleoresin capsicum” we see listed on the cans of pepper spray?

Before proceeding, a short vocabulary lesson is in order. Capsicum is the Latin word for pepper and is the genus-level designation for all peppers used in seasonings for hotness. Hence, oleoresin (oleo = oil and resin= extract obtained from a plant) capsicum (pepper) means quite literally "pepper extract in oil". When jalapenos (moderately hot), habaneros (fiery hot), or even bell peppers (no hotness at all) are finely ground, this pepper slurry mixed in vegetable oil literally becomes 'oleoresin capsicum'.

Oleoresin capsicum (abbreviated O.C.) is the oily mixture produced when the burning compounds, which naturally occur in hot red peppers, are extracted. O.C. is comprised primarily of a) carotenoids: the red pigments found in many vegetables, b) vegetable oils and, c) capsaicinoids, the compounds responsible for pungency. There are over 25 capsaicinoid compounds found in O.C., but only 3 are considered ‘active ingredients’ and are responsible for the "heat" or pungency of the solution: capsaicin, nordihydrocapsaicin and dihydrocapsaicin. The other capsaicinoids, while comprising a larger percentage of the O.C., are relatively inert with respect to their ability to elicit the burn response.

Above it was stated that OC is the oily mixture extracted from red peppers. But red peppers aren’t naturally oily. The oil in OC results from the process used to extract the active ingredient from ground peppers. Since capsaicinoids are highly soluble in oil, the slurry of freshly ground red peppers is saturated with vegetable oil then strained through fine sieves, leaving behind much of the plant cell wall matter. Some manufacturers use volatile solvents in combination with vegetable oil during the extraction process to reduce viscosity. This shortens the filtering time. Afterwards the volatile solvents are removed.

This capsaicinoid-rich oil is a deep red hue, however, because carotenoids in the peppers are too fine for the sieves to remove. Most oleoresin capsicum originates from red pepper growers in India and Africa. Further extraction and separation of capsaicin from the oil is expensive and since the target industry for most of this product is the commercial food business, vegetable oil is a choice medium for export and sale. Commercial food companies use OC to add hotness to everything from chili to salsa. The pepper spray manufacturing sector purchases this “food grade OC” in its thick, red state and combines it with a carrier chemical which dilutes and thins it out. Then, by adding a propellant to the canisters containing this mixture the contents can be expelled as “pepper spray”.