Complex sentence: Most anthroposophic preparations are highly diluted, like homeopathic remedies, and while this means they are completely harmless in themselves, using them in place of conventional medicine to treat serious illness risks severe adverse consequences.
Split into simpler sentences: Most anthroposophic preparations are highly diluted, like homeopathic remedies. This means that, while they are completely harmless in themselves, using them in place of conventional medicine to treat serious illness carries a risk of severe adverse consequences.