Complex sentence: Flower spikes can be used internally for headaches, irritability, feverish colds and nausea, and externally used for wounds, rheumatic pain and as an insect repellent.
Split into simpler sentences: Flower spikes can be used internally for headaches, irritability, feverish colds and nausea. Externally used for wounds, rheumatic pain and as an insect repellent.