There are no known contraindications for the Melmak bone growth stimulator. Worthy of note is that both safety and effectiveness have not been studied in individuals whose bones are still growing, pregnant and/or nursing women, people with pacemakers, patients with cancer or patients with poor blood circulation or clotting issues. There have been several cases (very few) where individuals are sensitive to the gel. Alternatives can be found for these individuals. It is recommended that you consult your doctor at all times.