ailanthus,

Why do you think they wouldn't enter the bloodstream? Everything that enters the digestive tract is broken down and filtered into the bloodstream except for foecal matter that is pooed out. It is via the bloodstream that chemical messengers are activated to stimulate muscle and nerve supply.

After preparation, homoeopathic medicines are dropped on to milk of sugar, or water/alcohol, and it is in either of these mediums that they are ingested, digested, and transfered to the bloodstream. Whether in a material or immaterial dose, a homoeopathic medicine is able to stimulate any organ, any nerve, any muscle, any bone, or any cell in the body. You can ingest a remedy by swallowing, or smelling (olfaction), or rubbing it into the skin. Ultra sensitive people can ingest a remedy by merely holding the remedy bottle in their hand. There are tests you can do that show physiological changes in a person when a remedy is held near them. I haven't a clue why anyone would need to inject a remedy except because of some rigid allopathic thinking.

Sulphur mineral baths is an example Hahnemann used of an external medicament causing long term suppression, which he was opposed to. As Anna said above, Hahnemann also advised against topically applying a remedy to a skin eruption, this mode of transmission he deemed to be too direct, I believe, which would only serve to cause a disruption to the healing process.