I have chronic osteoarthritis I use bengay daily and it makes me feel cold. Using the heating pad seems to help, yet I read on the label not to use with a heating pad. Why is this a potential problem?
The advisory is because bengay and other topical analgesics numb feelings of pain and heat. The worry is that the heating pad might get too hot and you could burn yourself and not know it if you're using bengay on that spot.
The heating pad doesn't interfer with bengay's effectiveness at all. It's purely a precautionary measure. Here's what the Bengay site says...
The FDA and Consumer Product Safety Commission have issued a public health advisory on the use of heating pads. Among the individuals it identifies as being at particular risk for electric heating pad burn injuries are persons who may be unable to feel pain to the skin because of medication. It also indicates that a heating pad should never be used by a person who has skin that is not sensitive to temperature change. Since topical analgesics affect pain and skin temperature perception, they should not be used with a heating pad.