Why can't lice be washed away? - briefly
Lice attach to hair with clawed legs and a waterproof exoskeleton, allowing them to remain firmly anchored despite water flow. Washing alone cannot overcome these physical adaptations, so the insects persist after a rinse.
Why can't lice be washed away? - in detail
Lice cling to hair shafts with specialized claws that fit the contour of each strand. The claws interlock with the cuticle of the hair, creating a mechanical grip that water alone cannot break. This attachment is reinforced by a secretion of silk‑like material produced by the female, which cements the eggs (nits) to the shaft and adds further resistance to mechanical forces.
The exoskeleton of a louse consists of a hardened, hydrophobic cuticle. Water does not penetrate this layer, so the insect remains buoyant and retains its grip during rinsing. The cuticle’s low surface energy reduces adhesion to liquid, preventing the insect from being dislodged by the shear forces generated in a typical shower.
Washing exposes lice to brief, low‑intensity turbulence. The forces generated by standard faucet flow are insufficient to overcome the combined strength of claw interlocking, silk cement, and cuticular rigidity. Consequently, the insects stay attached while the surrounding water is easily removed.
Effective removal requires either:
- Mechanical disruption using a fine‑toothed comb to slide over the hair and physically pull the insects and nits from the shaft.
- Chemical treatment with pediculicidal agents that dissolve the cement or incapacitate the nervous system, allowing subsequent combing or washing to clear the infestation.
Therefore, ordinary rinsing fails because the lice’s anatomical adaptations and the properties of their protective structures resist the modest mechanical action of water alone.