If you're able to hit the bear in the face, you're in business. Most likely the bear will make an instant, confused retreat. It won't knock a bear out, but it will definitely make it forget it wants to eat you. Capsaicin has the same effect on bears that it does on humans. They'll feel an instant burning sensation wherever you hit them, so just like humans, it's best to get them in the face. The eyes, nose and lungs will all burn like fire, causing the mucous membrane tissues to swell.
A face hit almost guarantees temporary blindness and big-time breathing problems. But the good news is that the sting will eventually subside and by that time, either you or the bear are long gone. You have all your limbs in tact, and the bear suffers no permanent damage. The same can't be said about bullets.
What can be said for bullets? They don't always thwart an attack. The U.S. Fish and Wildlife Service investigated human and bear encounters from 1992 to 2005 and found that people who defended themselves with firearms were injured about 50 percent of the time by the bear. People who used the bear spray escaped injury 98 percent of the time, and the few injuries they suffered were far less severe than those in the gun-toting realm. Why? Because it's difficult to stop a bear with a gun and wounded bears are more likely to become even more aggressive.
Another study was performed by Thomas Smith, a bear biologist from Brigham Young University. After analyzing 20 years of bear incidents, he found that bear spray was effective 92 percent of the time, compared to 67 percent for guns. Add to this that you can't bring guns into many national parks, and it seems like the spray is the best way to go.
Research has shown that it takes an average of four direct hits with a bullet to stop a bear [source: Science Daily]. Do you feel like you're a good enough shot to pull this off when a 600-pound (272-kg) grizzly is coming at you at 35 miles per hour (56 kph)? Accuracy isn't nearly as important with bear spray since you're shooting a wide cloud of smoke at your threat. Wind may be an issue, but the Wildlife Service study found that it only affected the shot 7 percent of the time and in each case, the spray still reached the bear. If you happen to shoot yourself or a friend as well, the effect of the bear spray will be the same as human pepper spray and will wear off after a few hours of discomfort.