Food grade is pure with no stabilizers. It seems purity is more important with ingestible H2O2. Here is an article excerpt I found on this site:
http://www.h2o2.com/intro/faq.html#4
4. What are H2O2 stabilizers and will they affect my application?
Most commercial grades of H2O2 contain chelants and sequestrants which minimize its decomposition under normal storage and handling conditions. In some applications (e.g., copper etching or cosmetic formulations) a high degree of stabilization is needed; whereas, in others (e.g., drinking water treatment or semiconductor manufacture) product purity is more important. For most environmental applications, H2O2 stabilization does not affect product performance.
The types of stabilizers used in H2O2 vary between producers and product grades. Colloidal stannate and sodium pyrophosphate (present at 25 - 250 mg/L) are the traditional mainstays, although organophosphonates (e.g., Monsanto’s Dequest products) are increasingly common. Other additives may include nitrate (for pH adjustment and corrosion inhibition) and phosphoric acid (for pH adjustment). Certain end-uses -- which depend on the bleaching ability of H2O2 in alkali – utilize colloidal silicate to sequester metals and thereby minimize H2O2 decomposition
And another:
http://www.h2o2-4u.com/grades.html
With this information in mind, I have read on H2O2 therapy sites that to stabilize diluted food grade H2O2 one must only refrigerate it. However, if you use it daily for whatever applications you will have used it up before it becomes unstable losing it's potency. Then, that question becomes moot. So, if you are concerned about the chemicals in 3% in the drug store use the food grade. 'Nough said, no?;)
" Then it was, then again it will be. And though the course may change sometimes rivers always reach the sea." Robert Plant