Science has proven that the cat’s purr has many healing frequencies. Cats purr at frequencies ranging from 25- 150 hz. Recent research indicates that frequencies which lie between 25-150 hz have been instrumental in healing muscles, bones, tendons, and ligaments, and helpful in relieving pain. In fact, researchers found that application of vibrational frequencies in this range helped to relieve pain in over 80 % of the participants with both acute and chronic pain.  Dr. Clinton Rubin researched and discovered that frequencies between 25 — 50 hz can increase bone density by as much as 20 %.

This explains why cats don’t just purr when they are happy. Cats also purr when they are injured and/or close to death. The vibrating frequencies induce a blissful meditative state, release endorphins, and a variety of healing chemicals and vibes.

source: https://www.scientificamerican.com/article/why-do-cats-purr/

source: http://animalwellnessmagazine.com/can-your-cats-purr-heal/