The question is not of small doses, but it is relying on the potency of the medicine.
There’s this thing, that many doctors and homoeopaths spend most of the time studying. It’s called the “Water Memory”.
Water memory is a logic, that considers water to have a memory, just like us human beings, for example.
It states that whenever any substance or chemical touches water, it leaves a lasting impression on the water.
Homoeopathy remedies and medicines are completely based on this theory of “Water Memory”. It doesn’t even matter whether or not a single molecule of the substance is present after it is diluted in water, or alcohol ( Two most common solvents used in homoeopathy medicines). What matters is that, the more diluted is the medicine, and lesser the trace of the original substance in the medicine, the better is the effectiveness of the remedy!