Mace spray is a self-defense aerosol designed to temporarily incapacitate an attacker by causing intense pain, tearing, and difficulty seeing. The name originally referred to a specific product invented in the 1960s by Alan Lee Litman, but it has since become a generic term people use for almost any personal defense spray, much like “Band-Aid” for adhesive bandages. Today’s Mace brand products are quite different from the original formula, which causes some confusion worth clearing up.
Original Mace vs. Modern Pepper Spray
The original “Chemical Mace” used an ingredient called chloroacetophenone, a synthetic tear gas compound designated CN by the military. CN works primarily through pain compliance: it triggers burning and stinging on the skin’s surface nerve endings, especially on the face, and causes tearing and irritation in the eyes. The key limitation of CN is that it relies on a person’s ability to feel pain. Someone who is heavily intoxicated, on certain drugs, or in an extreme mental state may not respond to it effectively.
Pepper spray, by contrast, uses capsaicin, the same compound that makes hot peppers burn. Rather than just causing pain, capsaicin triggers involuntary physical reactions. It inflames the throat lining and temporarily restricts airway size, forces the eyes shut by dilating the capillaries in the eye area, and causes visible redness that lasts 30 to 60 minutes. Respiratory function typically returns to normal within 10 to 45 minutes. Because these are inflammatory responses rather than pain responses, pepper spray works on people with elevated pain tolerance, including those under the influence of alcohol or drugs.
Modern Mace brand products now contain pepper spray (OC) rather than the original CN formula, or sometimes a combination of both. So when someone buys a canister labeled “Mace” today, they’re almost certainly getting a pepper-based product.
How It Works in the Body
Both CN tear gas and pepper spray target specific pain-sensing channels in nerve endings throughout the skin, eyes, and airways. CN and its relatives activate one type of channel that creates an intense sensation of scalding heat. These channels are so sensitive to tear gas compounds that the agents are roughly 10,000 times more potent on them than natural irritants.
Capsaicin in pepper spray hits a related but different channel found in peripheral sensory nerves across all organs, including the skin, the surface of the eye, and the mucous membranes of the upper and lower airways. When activated, this channel triggers both pain and a cascade of inflammation, which is why pepper spray causes swelling and involuntary eye closure rather than just a burning sensation. Contact lens or glasses wearers are not protected; the spray affects them equally.
Spray Patterns and Range
Defense sprays come in several delivery formats, each suited to different situations. Stream sprays fire a focused liquid line, similar to a water gun. Personal-sized stream canisters typically reach 10 to 12 feet, while larger police-model versions can reach about 15 feet. Streams are more wind-resistant and less likely to blow back toward you, but they require better aim.
Gel sprays travel farther, reaching 20 to 25 feet depending on canister size. The gel sticks to skin on contact, reducing the chance of cross-contamination to bystanders. Fogger sprays release a wide mist that’s easier to aim in a panic. Bear deterrent foggers can reach up to 40 feet and empty their canister in about 9 seconds, designed for large, fast-moving animals at a distance.
Legal Restrictions by State
Mace and pepper spray are legal for civilian self-defense across all 50 states, but many states impose limits on canister size, concentration, or how you can purchase them. A few notable examples:
- New York and New Jersey: Canisters cannot exceed 0.75 fluid ounces. New York also caps the active ingredient strength and prohibits online shipping to the state.
- California: Maximum container size is 2.5 ounces.
- Florida: Capped at 2 ounces.
- Massachusetts, Alaska, and Hawaii: Online shipping of pepper sprays and gels is prohibited, meaning you need to buy locally.
- Michigan: Limits both the amount of tear gas (CS) and the concentration of pepper extract (OC) to no more than 18%.
If you plan to fly with a defense spray, the TSA allows one container of up to 4 fluid ounces in checked baggage only, never in a carry-on. The canister must have a safety mechanism to prevent accidental discharge, and sprays containing more than 2 percent tear gas (CS or CN) by mass are banned from checked bags entirely. Some airlines add their own restrictions on top of TSA rules, so check before you pack.
Shelf Life and Storage
Most defense spray canisters last two to four years before the pressurized propellant begins to leak, reducing both the spray distance and the force of the stream. Smaller keychain-sized canisters are especially prone to pressure loss and may need replacement every 12 to 18 months if you test-spray them periodically. Extreme heat and cold accelerate this degradation, so storing a canister in a car’s glove box through summer or winter shortens its usable life. Most canisters print an expiration date on the bottom or side.
What to Do After Exposure
If you or someone nearby gets sprayed, the priority is moving to fresh air and flushing the affected skin and eyes with large amounts of cool water. Blinking rapidly helps clear the irritant from the eyes. Avoid rubbing the affected area, since the oily base of pepper spray spreads easily to other parts of the body. Remove and bag any clothing that contacted the spray to prevent re-exposure.
You may have heard that milk, baby shampoo, or antacids help neutralize the effects. A 2008 study comparing these home remedies found no evidence they worked better than plain water, and a 2018 randomized trial confirmed that baby shampoo offered no advantage over water alone for relieving symptoms. Avoid using soap near the eyes, as it can add irritation. Emergency responders sometimes use saline solution or specialized chemical wash products, but for most people, thorough flushing with water and patience are the most effective approach. The worst of the effects typically resolve within 45 minutes to an hour.