Pepper spray is a non-lethal weapon designed to spray into the face of an attacker. Pepper spray affects the mucous membranes, causing capillaries in the eyes to instantaneously dilate to the point of temporary blindness. Tissues lining the bronchial tube also swell, making it difficult for the attacker to get extra oxygen. A blast of pepper spray affects the eyes, throat, nose and lungs, with the effects lasting up to 90 minutes.

Because pepper spray is an inflammatory substance, it affects even those who might not register pain, like psychotics, drug addicts or inebriated individuals. It's also effective against an attacking animal, and is carried by many mail carriers. This benefit has become more relevant as newly developed neighborhoods encroach on rural land, creating clashes between people and wildlife. Joggers who take rural trails near their homes can benefit from carrying pepper spray.

Pepper spray is made from hot cayenne peppers. The active ingredient is called oleoresin capsicum (OC). Sprays that are made with 2-10% of OC incapacitate faster than higher concentrations. Some sprays also include an indelible dye to mark the attacker.

Hot cayenne peppers, like jalapenos, chiletpins, and habaneros, are chili peppers. All of these peppers contain an alkaloid called capsaicin. Capsaicin is tasteless and odorless, but just 1 part per ten million can be detected by humans in the form of heat.

Capsaicin is produced in a gland just below the stem of the pepper. This spot is about 16 times stronger than any other part of the plant. The active ingredient in pepper spray is derived from this area.

The power or heat value of capsaicin is expressed in Scoville Units which can be determined through a test called high-performance liquid chromatography. While a bell pepper rates a zero on the heat scale, a jalapeno hits the 8,000 mark and a habanero jumps to 350,000. Good pepper spray rates somewhere around 5,300,000 on the heat scale, beat only by pure capsaicin at 16,000,000.

While pepper spray is an inflammatory agent, Mace and tear gas are irritants, and do not fall under the same laws as pepper spray. Pepper spray is legally purchased over the counter in most states and comes in various size canisters, some small enough to hang on a key chain.

If you have any questions about the legality of pepper spray in your state, contact your local police department.