Mace spray today is primarily made of oleoresin capsicum (OC), the same compound that gives chili peppers their heat. This active ingredient is dissolved in a liquid carrier and packaged in a pressurized canister with a propellant gas. The original Mace formula from the 1960s used a completely different chemical, and the name has stuck even as the product changed. Here’s what’s actually inside modern canisters and how each component works.
The Original Mace Formula
The name “Mace” originally referred to a specific chemical compound called phenacyl chloride, also known by its military designation CN. The acronym MACE itself came from its full chemical name: methylchloroform chloroacetophenone. CN is a synthetic irritant manufactured by chlorinating acetophenone, and it was the standard tear gas agent for decades.
CN fell out of favor because it has the highest toxicity among common tear gas agents when measured by the threshold needed to cause irritation. A newer synthetic tear gas called CS (o-chlorobenzylidene malonitrile) replaced it in many military and law enforcement applications because CS is effective at lower concentrations with a wider margin of safety. Most consumer “Mace” products today have moved away from both CN and CS entirely, relying instead on pepper-based formulas.
What Modern Mace Spray Contains
The active ingredient in nearly all current self-defense sprays, including those sold under the Mace brand, is oleoresin capsicum. OC is a natural extract from hot peppers that contains capsaicinoids, the molecules responsible for the burning sensation. Law enforcement and consumer products typically range from 500,000 to 5 million Scoville Heat Units, though the actual intensity you’d feel depends on how much the extract is diluted in the final product.
Some formulas blend OC with CS or CN tear gas for a combined effect. Others use OC exclusively. The label will usually specify which active agents are present and their concentration.
Carrier Solvents
Capsaicinoids don’t dissolve well in water, so manufacturers use chemical solvents to keep the active ingredient in a sprayable liquid form. Common carriers include ethanol, isopropanol (rubbing alcohol), propylene glycol, and secondary butanol. Some older or industrial formulations use kerosene, acetone, or methylene chloride. The carrier evaporates quickly after the spray hits a target, leaving the irritant behind on the skin and in the eyes.
Propellants
The canister needs pressurized gas to push the liquid out in a stream, cone, or fog pattern. Nitrogen and carbon dioxide are the most common propellants. Some products use hydrocarbons like propane or butane, while others rely on tetrafluoroethane, the same gas used in some aerosol products. The propellant choice affects spray distance and pattern but doesn’t contribute to the irritant effect.
UV Marking Dye
Many defensive sprays include an invisible ultraviolet dye mixed into the formula. This dye is invisible to the naked eye but glows under ultraviolet light, allowing law enforcement to identify a suspect after an encounter. The dye can remain on skin and clothing for several days depending on conditions and the amount sprayed.
How OC Works in the Body
Capsaicin targets a specific type of pain receptor called TRPV1, found on nerve endings throughout the skin, eyes, and respiratory tract. TRPV1 is the same receptor your body uses to detect heat from hot food. When capsaicin binds to these receptors, it forces them open, flooding the nerve cell with calcium and sodium ions. This triggers an intense pain signal along the same pathways your body uses to warn you about burns or injury.
The result is immediate and involuntary: the eyes slam shut, tears pour out, the nose runs, and breathing becomes difficult. The reaction is so strong because TRPV1 receptors are densely concentrated in the mucous membranes of the eyes, nose, and throat. Your body essentially responds as if those tissues are being burned, even though no actual thermal damage is occurring.
How Long the Effects Last
Symptoms hit within 20 to 60 seconds of exposure, starting with the eyes and lungs. In most cases, the worst effects are self-limited and fade within 10 to 30 minutes once you’re away from the source. Visual acuity typically returns to normal in that same window.
Some effects linger longer. Redness around the eyelids and sensitivity to light can persist beyond the initial recovery. A runny nose and excess salivation may last about 12 hours, and headaches can stick around for up to 24 hours. Skin redness usually clears within an hour, but blistering or more severe skin reactions can take up to four days to fully resolve. In some people, delayed skin reactions like contact dermatitis appear 12 to 24 hours after exposure.
Legal Concentration Limits
Regulations vary by state and country, but federal rules offer a baseline. The TSA allows one container of mace or pepper spray up to 4 fluid ounces (118 ml) in checked luggage only, provided it has a safety mechanism to prevent accidental discharge. Products containing more than 2 percent tear gas (CS or CN) by mass are prohibited even in checked bags. Pepper spray is never allowed in carry-on luggage.
State laws govern concentration limits and canister sizes for everyday carry. Some states cap OC concentration at 10 percent, while others have no specific limit. A few states and most countries outside the U.S. restrict or ban civilian possession entirely, so the legal landscape depends heavily on where you are.