The term OC (oleoresin capsicum) is a horticultural term, which refers to chili peppers. There are many different kinds of chili peppers ranging from jalapeños, chiletpin, and cayenne to habañeros. They all have one thing in common. They all contain a substance that is very powerful -- an alkaloid called capsaicin (cap-say-a-sin). Just a single drop of tasteless and odorless capsaicin in 100,000 drops of water and the heat can be noticeable. In fact, capsaicin can be detected by humans at one part per ten million!
One of the biggest misconceptions about pepper spray is that the higher the percentage, the hotter and better it works. In most cases this could not be further from the truth. Most of the best, fastest incapacitating sprays in the world are from 2%-17%. The lighter the fluid, the faster it penetrates the membranes. The percentage has nothing to do with the actual SHU or "hot" in the spray. Also, thicker sprays can inflame the skin area more and last longer with this unnecessary inflammation. A good spray will put the attacker down and out allowing you to escape or take control of the situation.
Because it is an inflammatory, rather than an irritant, pepper spray is effective against attackers who may not feel pain such as psychotics, drunks and drug abusers. Pepper spray has proven itself to be the ABSOLUTE BEST DETERRENT available for attacking dogs and wild animal control. Another major advantage of pepper spray is that it is not volatile and will not emit a lot of fumes like tear gases.