The active ingredient in pepper spray is oleoresin capsicum, a concentrated oily extract drawn from hot chili peppers. Within that extract, the compounds that actually cause pain and irritation are capsaicinoids, a family of chemicals naturally produced by pepper plants. But a canister of pepper spray contains more than just capsaicinoids. Solvents, propellants, and other additives make up the bulk of the liquid, and those secondary ingredients carry their own risks that are often overlooked.
Capsaicinoids Are the Core Irritant
Oleoresin capsicum, usually abbreviated OC, is the ingredient listed on virtually every commercial pepper spray canister. OC is not a single chemical but a crude extract containing dozens of compounds from chili peppers. The ones responsible for the burning sensation are capsaicinoids, which bind to pain and heat receptors in mucous membranes, skin, and the lining of the airways.1PubMed. Differentiation of oleoresin capsicum sprays based on their capsaicinoid profiles
Four capsaicinoids account for most of the irritant punch in a typical spray: capsaicin, dihydrocapsaicin, nordihydrocapsaicin, and nonivamide.2PubMed. The impact of time and storage conditions on samples containing OC pepper sprays on the quantitative ratios of capsaicinoids Capsaicin and dihydrocapsaicin are usually the most abundant and most potent of the group. Their exact proportions vary from one product to another, depending on which pepper cultivar was used and how the extraction was done.1PubMed. Differentiation of oleoresin capsicum sprays based on their capsaicinoid profiles This is why two canisters that both say “10% OC” on the label can feel very different in intensity: the total capsaicinoid concentration inside that 10% extract can differ substantially.
Labels often quote an OC percentage or a Scoville Heat Unit rating, but neither number tells you much about how painful the spray will be. What matters is the concentration of the major capsaicinoids themselves, and most consumer labels do not disclose that figure. Forensic chemists can distinguish one brand’s spray from another by looking at the ratios of these four capsaicinoids, which act almost like a chemical fingerprint for the product.
Solvents, Propellants, and Other Ingredients
Capsaicinoids are oily and do not dissolve easily in water. A canister needs a solvent to keep them in a sprayable solution and a propellant to push that solution out at pressure. Common solvents include isopropyl alcohol, ethanol, water, and propylene glycol. Common propellants include propane, butane, and older options like certain chlorinated compounds.3Human Factors and Mechanical Engineering for Defense and Safety. Counterfeit Pepper Spray: a Case Report Most modern formulations have shifted toward less toxic, less flammable carriers, though nearly every formula still contains some proportion of alcohol to keep the mixture from freezing in cold weather.
These non-capsaicinoid ingredients can create hazards of their own. The alcohol content makes many pepper sprays flammable, which is a real concern when a spray is deployed near a Taser or other electrical device. The propellants, while generally inert in small quantities, add to the chemical cocktail that lands on skin and gets inhaled. And the quality of these secondary ingredients is not always well controlled, especially in budget or unregulated products.
The Problem with Unregulated Formulations
Quality varies enormously across the pepper spray market. A forensic analysis of sprays sold in one market found methanol used as a carrier solvent, a substance that is genuinely toxic and has no justification in a self-defense product when safer alternatives exist.3Human Factors and Mechanical Engineering for Defense and Safety. Counterfeit Pepper Spray: a Case Report Methanol can cause acute poisoning through skin absorption or inhalation. The researchers noted this posed a risk not only to the people being sprayed but also to law enforcement officers who handle these products regularly.
Civilian storage and shelf life are also poorly studied. Technical questions about thermal stability, expiration dates, and long-term safety of stored canisters have received surprisingly little formal attention in the scientific literature.4J. Braz. Chem. Soc.. Perspectives and Applications of Natural Products as Civilian Defense Devices Over time, propellant gas leaks through canister seals. A study of bear spray canisters found brands lost anywhere from about 0.7 to 1.9 grams of weight per year, presumably from escaping propellant.5The Journal of Wildlife Management. An Investigation of Factors Influencing Bear Spray Performance An older canister may still contain capsaicinoids but lack the pressure to deliver them effectively, or it may produce a weak, sputtering spray that puts the user in danger if they are relying on it for protection.
What Happens When Pepper Spray Hits You
Capsaicinoids work by activating a receptor on nerve endings called TRPV1, the same receptor your body uses to detect actual heat. When capsaicin binds to it, the receptor fires as though your tissue is being burned, even though no thermal damage is occurring. The result is intense, immediate pain, especially on wet mucous membranes like the eyes, nose, mouth, and airways, where capsaicinoids penetrate most easily.6PubMed Central. Capsaicin: Current Understanding of Its Mechanisms and Therapy of Pain and Other Pre-Clinical and Clinical Uses
In the eyes, the response is near-instantaneous: severe pain, involuntary clamping of the eyelids shut, heavy tearing, and blurred vision. A controlled study of volunteers exposed to OC spray found that all subjects reported significant pain, vision blurring, and tearing within ten minutes. Most of those symptoms were much improved by one hour.7PubMed. Clinical effects of oleoresin capsicum (pepper spray) on the human cornea and conjunctiva Roughly a fifth of those eyes showed small erosions on the corneal surface, though no full corneal abrasions were identified in that particular study.
Skin contact produces burning pain, redness, swelling, and itching. In a review of over 3,600 pepper spray exposures recorded by the California Poison Control System over a decade, skin contact was the most common route of exposure, accounting for about 60% of victims. Most had minor, self-limiting symptoms, but around 3% of those with skin exposure reported more serious reactions including persistent skin inflammation, chemical burns, or blistering.8Hong Kong Medical Journal. Clinicopathological effects of pepper (oleoresin capsicum) spray
Eye Injuries Beyond the Initial Burn
The immediate pain from pepper spray in the eyes is temporary, but the risk of lasting damage is not zero. A review of 100 pepper spray exposure cases found that seven patients had sustained actual corneal abrasions, a more serious injury than the superficial erosions seen in the controlled volunteer study.9PubMed. Corneal abrasions associated with pepper spray exposure The researchers concluded that corneal abrasions are “not rare events” after pepper spray exposure and recommended that all exposed patients receive a proper eye examination if abrasions cannot be ruled out clinically.
The discrepancy between the controlled study and the real-world case review is telling. In a laboratory setting, subjects were sprayed in a measured way and decontaminated promptly. In real encounters, the spray often hits at close range, victims rub their eyes instinctively, and decontamination is delayed. Those factors likely drive a higher rate of corneal injury. People who wear contact lenses face additional concern because the lens can trap capsaicinoid residue against the cornea, prolonging exposure.
Respiratory Effects and At-Risk Groups
Inhaling pepper spray triggers coughing, choking, a sensation of shortness of breath, and sometimes gagging or vomiting. A mass exposure incident in a shopping complex sent 13 people to a hospital emergency department with a range of symptoms including eye and skin irritation, nausea, vomiting, and dizziness.10Hong Kong Journal of Emergency Medicine. Mass Casualty Incident Involving Pepper Spray Exposure: Impact on the Emergency Department and Management of Casualties In an open outdoor space, these effects are usually short-lived. In enclosed spaces like hallways, cars, or jail cells, the concentration of airborne capsaicinoids can be much higher and the exposure longer, which raises the severity of symptoms considerably.
People with chronic lung conditions face particular danger. Capsaicin can cause bronchoconstriction, the narrowing of airways that makes breathing difficult. A toxicology review noted that individuals with chronic obstructive lung disease may be hypersensitive to this effect, though the researchers cautioned that the experimental data on asthmatics and pepper spray exposure are still too limited to draw firm conclusions.11PubMed. Toxicologic evaluation of pepper spray as a possible weapon for the Dutch police force: risk assessment and efficacy The cardiovascular system is affected too: capsaicin can cause a temporary spike in blood pressure, usually less than 10 mmHg, that returns to normal within about two hours.12Austin Critical Care Journal. Cardiac Arrest in a Young Patient Triggered due to Pepper Spray: A Case Report For someone with severe heart disease or uncontrolled hypertension, even a modest spike combined with the stress of the encounter could be dangerous.
Deaths and Severe Outcomes
Deaths following pepper spray exposure do occur, though establishing a direct causal link is difficult. A literature review of injuries and deaths after OC spray use found that when deaths happened in close proximity to pepper spray deployment, common contributing themes were present, including drug intoxication, pre-existing heart conditions, physical restraint, and excited delirium. The review noted that OC spray is “typically associated with decreased odds of both subject and deployer injury” and that injuries, when they do occur, tend to be minor. But the researchers also stressed that the evidence base is thin enough that one must be cautious about making definitive claims about the safety of OC spray in relation to deaths.13The Police Journal: Theory, Practice and Principles. Injuries and deaths proximate to oleoresin capsicum spray deployment: A literature review
The honest assessment is that pepper spray is unlikely to kill a healthy person in a typical outdoor encounter, but the risk escalates with pre-existing health conditions, enclosed spaces, prolonged exposure, physical restraint that limits breathing, and the use of other force simultaneously. These compounding factors make it very hard to attribute any single death purely to the spray rather than to the overall circumstances.
Decontamination After Exposure
If you are sprayed, the instinct is to look for a magic remedy. Various home treatments circulate online, including baby shampoo solutions, milk, and antacid mixtures. A randomized controlled trial tested whether a baby shampoo solution relieved OC-related eye and respiratory discomfort better than plain water. It did not. There were no meaningful differences in discomfort between the baby shampoo group and the water-only group at any time point measured.14PubMed Central. Baby Shampoo to Relieve the Discomfort of Tear Gas and Pepper Spray Exposure: A Randomized Controlled Trial
The most practical advice is straightforward: move to fresh air, remove contaminated clothing, and flush affected skin and eyes with large amounts of clean water for at least 15 to 20 minutes. Do not rub your eyes or face, because that grinds the oily residue further into your skin and mucous membranes. Since capsaicinoids are oil-based and do not dissolve well in water, a mild soap can help lift residue from skin, but the eyes should be flushed with water only. Contact lenses should be removed as soon as safely possible. Most symptoms resolve on their own within 30 to 60 minutes once the capsaicinoids are washed away, though lingering skin sensitivity can persist for hours.
How OC Compares to Synthetic Tear Gases
Pepper spray is often lumped together with tear gas, but the chemicals are different. The two most common synthetic tear gases are CS (used by military and police worldwide) and CN (an older compound). OC is natural in origin, extracted from peppers, while CS and CN are manufactured synthetically.15PubMed. Comparative safety evaluation of riot control agents of synthetic and natural origin A fourth agent, PAVA, is a synthetic version of capsaicin sometimes used in law enforcement sprays instead of or alongside natural OC.
All of these chemicals irritate mucous membranes, but their toxicity profiles differ. A comparative safety evaluation found that OC and PAVA were more acutely toxic than the synthetic agent CR when measured by oral toxicity in animal models.15PubMed. Comparative safety evaluation of riot control agents of synthetic and natural origin On the other hand, a review of irritation thresholds found that CN produced irritation fastest, followed by CS, with OC being the least irritating of the three by that particular measure.16Proceeding International Conference on Religion, Science and Education. Literature Review: Effect of Exposure to Weapon Tear Gases CN, CS, and OC on Toxicity These seemingly contradictory findings reflect different ways of measuring harm. Irritation speed is not the same thing as overall toxicity, which involves factors like organ damage, dose-response curves, and long-term effects. The picture is genuinely complicated, and no single riot control agent is unambiguously “safer” than the others across all scenarios.
One distinction that matters practically: CS and CN tend to be deployed as fine powders or aerosols that linger in the air, while OC sprays are typically liquid streams or cones directed at an individual. That means OC is generally more targeted, but it can still cause mass exposure events when used in enclosed or crowded spaces.
Why the “Natural” Label Is Misleading
Because OC comes from peppers, it is sometimes marketed as a “natural” self-defense product, implying safety. This is misleading. The capsaicinoid concentrations in commercial pepper spray are orders of magnitude higher than anything you would encounter eating hot food. The extract is concentrated specifically to overwhelm pain receptors, and the delivery method, a pressurized burst aimed at the face, bypasses all the body’s normal defenses against capsaicinoid exposure (like dilution in food and gradual oral ingestion). The fact that capsaicin comes from a plant has no bearing on its safety profile at the concentrations used in defense sprays.
Capsaicin is, interestingly, used therapeutically in medicine as well, in low-dose topical creams for nerve pain and in research on pain modulation.6PubMed Central. Capsaicin: Current Understanding of Its Mechanisms and Therapy of Pain and Other Pre-Clinical and Clinical Uses The doses involved in medical use are a tiny fraction of what a pepper spray canister delivers, and the application is controlled and gradual. The same compound that relieves chronic pain at microgram doses causes acute agony at the milligram doses found in a self-defense spray. Context, concentration, and route of exposure make all the difference.
What You Cannot Tell from the Label
Consumer pepper sprays are regulated to varying degrees depending on jurisdiction. In some places they are sold with virtually no oversight; in others they require permits. But even where regulation exists, it tends to focus on who can buy and carry the product rather than on what is inside the canister. There is no universal standard requiring manufacturers to disclose the exact capsaicinoid concentration, the identity of the carrier solvent, or the propellant used.
The OC percentage on a label tells you how much of the liquid is pepper extract, but not how potent that extract is. A 2% OC spray made from extremely hot peppers could easily be more painful than a 10% OC spray made from milder varieties. Scoville ratings, when provided, are sometimes measured on the raw extract before dilution, making them essentially meaningless as a predictor of the spray’s actual effect. Without standardized testing, the consumer is largely left trusting the brand. Products from established manufacturers sold in regulated markets tend to be more consistent, but bargain or imported sprays can contain unexpected solvents or wildly inconsistent capsaicinoid levels, as the methanol case study demonstrated.3Human Factors and Mechanical Engineering for Defense and Safety. Counterfeit Pepper Spray: a Case Report
If you carry pepper spray for self-defense, the most practical thing you can do beyond choosing a reputable brand is to check the expiration date. A canister that has been sitting in a glove compartment for years may have lost enough propellant to deliver a weak, ineffective spray at exactly the wrong moment. Replacing canisters every two to three years, or sooner if the manufacturer recommends it, is a reasonable precaution given the measured propellant loss rates over time.5The Journal of Wildlife Management. An Investigation of Factors Influencing Bear Spray Performance