onions and garlic Contain sulfoxides and disulfides .... which can cause damage red blood cells and cause anemia .... however this is over a sustained period and large doses are needed .... onions are worse than garlic for this ... as reload says garlic powder is low grade and your dogs should be fine .... if you are really worried have a look at their gums if they are looking a bit pale then feed Beef liver .... it is full of iron, protein, B complex, and B12 .... this should bring the red blood cell count back up .............