Pepper spray contains three basic components: an active irritant derived from chili peppers, a liquid carrier that dissolves or suspends it, and a pressurized propellant that forces it out of the canister. The irritant is the part that causes pain, but the carrier and propellant make up most of what’s actually inside the can.
The Active Ingredient: Oleoresin Capsicum
The chemical that makes pepper spray work is oleoresin capsicum, commonly abbreviated OC. It’s an oily extract pulled from dried, ripe chili peppers of the species Capsicum annuum. Manufacturers use volatile solvents to strip the active compounds from the peppers, then distill and dry the result into a concentrated resin.
That resin is not a single chemical. It’s a complex mixture of over 100 compounds, but the ones responsible for the burning sensation belong to a family called capsaicinoids. These are the same compounds that make hot peppers hot when you eat them, just in a far more concentrated form. Capsaicin is the dominant one, making up about 70% of the capsaicinoid content. Dihydrocapsaicin accounts for another 20%. Together, those two compounds represent 80 to 90% of the active mixture. The remaining fraction includes three minor capsaicinoids: norhydrocapsaicin (about 7%), homocapsaicin (1%), and homodihydrocapsaicin (1%).
OC concentration in a canister typically ranges from 0.5% to 20% of the total formula. What matters more for potency, though, is the percentage of Major Capsaicinoids, the specific irritant compounds within that OC. Civilian and law enforcement sprays range from 0.18% to 1.33% Major Capsaicinoids. That small percentage is enough to be extremely effective.
Carriers and Propellants
OC on its own is a thick, oily resin. It needs a liquid carrier to dissolve or suspend it so it can be sprayed evenly. Common carriers include ethanol, isopropanol (rubbing alcohol), propylene glycol, and secondary butanol. Some formulations use petroleum-based carriers like kerosene, or solvents like acetone and methylene chloride. A citrus-derived solvent called d-limonene also shows up in some products.
The propellant is the pressurized gas that pushes everything out when you press the button. Nitrogen and carbon dioxide are the most common choices. Some canisters use hydrocarbon propellants like propane or butane, or a refrigerant gas called tetrafluoroethane. The propellant doesn’t contribute to the irritant effect, but it determines how far and how forcefully the spray travels.
How It Causes Pain
Capsaicinoids target a specific receptor on pain-sensing nerve endings called TRPV1. This receptor normally responds to heat and physical damage, so when capsaicin activates it, your nervous system interprets the signal as an intense burn, even though no actual thermal injury is occurring. The eyes, nose, mouth, and airways are packed with these nerve endings, which is why pepper spray is so effective on exposed mucous membranes.
When capsaicin binds to TRPV1, it opens a channel that floods the nerve cell with calcium. This triggers immediate, sharp pain and causes the surrounding tissue to release inflammatory signals. The result is rapid swelling of the eyelids, uncontrollable tearing, temporary blindness, a runny nose, coughing, and difficulty breathing. These effects typically peak within a few minutes and begin subsiding within 30 to 45 minutes, though some discomfort can linger for hours.
Interestingly, after the initial burst of pain, prolonged or high-dose capsaicin exposure produces a refractory period where the affected nerves become temporarily unresponsive, not just to capsaicin but to other painful stimuli including heat. This “desensitization” effect is actually the basis for capsaicin pain-relief creams, which use tiny doses of the same compound to dull chronic pain over time.
How Potency Is Measured
Pepper spray potency is often described in Scoville Heat Units (SHU), the same scale used to rate hot peppers. For context, a jalapeño registers around 2,500 to 8,000 SHU. Pepper spray operates in a different universe. Civilian sprays typically fall between 500,000 and 2,000,000 SHU. Law enforcement versions range from 2,000,000 to 5,300,000 SHU. Bear spray, which is regulated by the EPA for use against charging wildlife, sits between 1,200,000 and 2,000,000 SHU.
Bear spray is actually less concentrated than most police-grade formulas, but it’s designed to discharge in a wide cloud over a longer range, which is more useful against a large animal at a distance. The SHU number alone doesn’t tell the whole story. Delivery method, spray pattern, and total volume all affect real-world performance.
Delivery Formats
The same OC formula can be packaged in different spray patterns, and the choice affects range, accuracy, and blowback risk. Stream sprays release a narrow, liquid jet that travels relatively far and resists wind. This is the most common type in personal defense products. Fogger sprays release a dense cloud of fine mist that’s harder to dodge but more susceptible to wind blowing back toward the user. Gel formulations shoot a thick, sticky substance that clings to skin and is harder to wipe off, reducing the chance of cross-contamination in enclosed spaces.
The OC concentration can vary across products regardless of delivery type. A gel and a stream from the same manufacturer might contain different percentages of oleoresin capsicum.
Respiratory and Health Risks
Pepper spray is classified as a less-lethal weapon, not a non-lethal one. The American Thoracic Society has warned that inhaling pepper spray, even during a single incident, can harm respiratory function and increase the risk of lung complications. For people with asthma or other underlying respiratory conditions, exposure can trigger severe bronchospasm.
Serious complications are uncommon but documented. Acute airway inflammation has in rare cases led to a collapsed lung (pneumothorax) or air leaking into tissue under the skin. Fatal outcomes carry an estimated risk of about 0.03%, typically involving people with pre-existing health conditions or prolonged exposure in confined spaces. The inflammatory response can also increase susceptibility to respiratory infections in the days following exposure.
Removing Pepper Spray After Exposure
Because OC is oil-based, it doesn’t wash away as easily as water-soluble substances. Still, cool water remains the best first response. If your eyes are affected, flush them with clean water for 10 to 15 minutes. A randomized controlled trial found that baby shampoo performs no better than plain water for eye decontamination, and there is no evidence that baking soda solutions or milk offer any advantage either.
For skin exposure, a cold shower lasting at least 20 minutes helps prevent the oil from spreading and irritating new areas. Avoid hot water, which opens pores and can intensify the burning. Remove contaminated clothing before showering, and avoid touching your face until your hands are thoroughly washed. The discomfort will fade on its own as the capsaicinoids break down and your nerve endings recover, but thorough flushing shortens that timeline considerably.
Shelf Life and Storage
Pepper spray has a usable life of roughly three to four years from the date of manufacture, though some formulations may begin losing effectiveness after one to two years. The capsaicinoids themselves are relatively stable, but the propellant can slowly leak from the canister over time, reducing spray distance and pressure. Heat accelerates this process. Storing a canister in a hot car or in direct sunlight can diminish both the propellant charge and the potency of the OC. Cool, dry storage extends shelf life. Most canisters print an expiration date on the label, and replacing them on schedule is the simplest way to ensure reliability.