A spot on to control parasites. This is a systemic product- i.e you put it on the skin but it absorbs into the blood stream.
It contains Selamectin. This is in the same group of drugs as Ivermectin. There is a group of dogs generally Collie types who are very sensitive to Ivermectin type drugs (Macrocyclic Lactones) Selamectin has been shown to be non toxic to Collies and their type even at five times normal dosage. Even so we feel avoidance of exposure to Macrocyclic Lactones in Collies and their type is the safe alternative.
It is absorbed through the skin so when you apply it to the back of the neck take care to get all of it onto the skin (see video)
Stronhold kills all sorts of parasites including fleas, ear mites and roundworms it is our first line treatment for Sarcoptic (Fox) Mange. We find it a safe and very useful product.