Is it true that eggs found 3cm away from the scalp are dead?
Most expert opinion is that eggs found more than 10-15 mm (1 to 1.5 cm) from the scalp are either hatched or dead. It is true that eggs are mostly laid close to the scalp – but this depends on the climate. When the ambient air temperature is close to (or exceeds) body heat, a female louse may lay eggs anywhere along the hair shaft, because the eggs will not depend on body heat to incubate. Even in cooler climates, heads that are hotter and perspire more will generally have eggs further away from the skin than cooler drier heads. Furthermore, a long hair that lays across & contacts the scalp for several centimetres, could have viable eggs at any point along it. These obvious, but widely unrecognised facts, could account for many puzzling re-infestations – especially in fair-haired people.
