Health.
what does the bruised, discolored, look on the skin at the ankle bone mean?
(picture included)

It could be a bruise or an infection

If it's a smaller child or infant, place one on the middle of the chest and on the child's back. (if it is a bigger child with enough room for two, place one on the upper right/your left of the chest, and one on the lower left/your right) the pads should never touch each other.