While most bears are not aggressive, there are instances when a bear, especially one that is hungry, sick or old will attack humans and their encounters can be deadly. When camping outdoors, one of the best bear repellents is prevention. It is possible to reduce the chance of an encounter with a bear by taking certain preventative measures when spending time outdoors such as knowing where bears are likely to reside and avoiding those areas and also, tying garbage and other foods into the trees, overhead of the bear's scope of smell.
One relatively effective bear repellent is pepper spray. Pepper spray utilizes the power of cayenne pepper to sting a bear and repel it away from humans. Most pepper sprays have a range that starts at approximately 15 feet and can spray up to 30 feet away. Be sure to know the laws that apply to using certain sprays before purchasing, as certain pepper sprays and MACE are banned in some states, even though they may be approved by the Environmental Protection Agency.
Pepper spray, when used as a bear repellent, is not likely to cause much harm to the bear, but will sting their eyes and usually cause them to leave an area where humans are. However, it is possible that certain sprays will not work on certain species of bears and may even cause a bear to become very aggressive. Also, a highly motivated bear may return to the area after only a few minutes. Other bears may leave for a period of time, such as a day or so and then return to the camping area, so it may be best to move onto another location after an encounter with a bear.
Pepper spray is most effective as a bear repellent when sprayed directly in the eyes. While some sprays may claim to work on the respiratory system, the eyes are the most effective place to spray as it will irritate the mucous of the bear's eyes. This means you may have to get in a relatively close proximity to a bear in order to aim correctly, so use extreme caution.