Most hypnotherapy websites include long lists of the many issues for which hypnotherapy can be used. Bottom line, a highly skilled hypnotherapist can deal effectively with virtually any issue a client presents. The 'issue' is not as important as the hypnotherapist's skill in accessing the client's subconscious mind to collaborate on a resolution to whatever energies or emotions underlie the issue.
Donald's work is effectively summarized as Hypnotherapy for Health & Happiness, Medical Hypnotherapy and Dental Hypnotherapy. A few issues are listed for each. But those are just the issues. To get a better idea of how Donald works, see his blog posts on issues like Sports Hypnosis or Grief.