Bunny lines are natural in some people. But they can also occur after a Botox injection for frown lines. There are different muscles involved in forming frown lines- the corrugator, proceris muscles between the brows. And when some people frown, the nasalis muscles are active. In most treatment sessions for frown line, the muscles between the brows are targeted. The nasalis muscles then become more visually prominent with the appearance of the bunny lines.
If you are thinking about undergoing a Botox treatment for frown lines, a board certified specialist can let you know if you are likely to have bunny lines or not.