Can such a small doses be effective ?

Homeopathic remedies are indeed very small doses. However, they are specially prepared doses which undergo a specific process including dilution of ingredients (called potentization), as well as a vigorous shaking (succussion).
Specially formulated homeopathic remedies are thought to resonate with the body, triggering a positive healing response. This response gently, and effectively, heals from the inside out.
The documented results from thousands of experienced homeopaths, and from millions of their patients, clearly show that these small, individualized doses produce profound health benefits.