I have written before about how we are the embodiment of our consciousness. What we think about ourselves, others and life will manifest in our physical experiences and symptoms. Allergies are often due to a perception of the world as an unsafe place. Back ache can be caused when we feel unsupported in the world.
Take a look at this interesting research about DNA and how we can create changes in our own DNA through our consciousness. (Please note that I do not specifically endorse this particular website or the healers but do find the articles informative).
To change your physical ailments become conscious of how you perpetuate them and consider how you can respond differently to life (or find someone to help you work with this). One way to figure out how your consciousness may be linked to your physical symptoms is to keep diary of your symptoms and what is going on at the time you experience your symptoms, as well as your thoughts and response to those circumstances. Just having the knowledge and awareness is the first step of stepping out of your pattern and freeing yourself from your particular story and experience of life.
You can empower yourself to manage your experience of your life and don't have to feel trapped and powerless. I will continue writing about this in more detail in the future so watch this space!