How does tar soap act on lice? - briefly
Tar soap eliminates lice by penetrating their cuticle, disrupting neural function, and causing rapid dehydration. It also infiltrates the protective layers of nits, inhibiting embryonic development and preventing hatching.
How does tar soap act on lice? - in detail
Tar‑based cleansing bars eliminate head‑lice infestations through several complementary mechanisms. The thick, viscous nature of the preparation creates a coating that occludes the respiratory spiracles on the insect’s abdomen, causing rapid asphyxiation. Simultaneously, the high‑temperature melt‑point of the tar matrix softens the cuticle, allowing the active constituents to penetrate the exoskeleton and disrupt neural transmission.
The primary active agents in the soap are polycyclic aromatic hydrocarbons derived from coal tar. These compounds possess lipophilic properties that dissolve the protective wax layer on the louse’s body, increasing permeability to the tar’s toxic constituents. Once the barrier is compromised, the hydrocarbons interfere with the insect’s mitochondria, impairing ATP synthesis and leading to metabolic collapse.
Eggs (nits) adhere tightly to hair shafts, protected by a robust chorion. The soap’s surfactant component reduces surface tension, allowing the tar to spread uniformly over the hair and reach the nits. The tar’s adhesive quality immobilizes the eggs, while the chemical action weakens the chorion, making the embryos vulnerable to desiccation and death.
Practical application follows a defined protocol:
- Wet hair thoroughly with warm water.
- Apply a generous layer of tar soap, ensuring complete coverage of scalp, hair, and all visible insects.
- Massage for 5–10 minutes to promote penetration.
- Leave the product on for 15–20 minutes; the prolonged contact maximizes respiratory blockage and chemical uptake.
- Rinse with warm water and repeat the treatment after 7–10 days to target newly hatched lice that escaped the initial exposure.
Safety considerations include avoiding contact with eyes and mucous membranes, as the irritant properties of coal‑tar derivatives can cause mild dermatitis. Users with known hypersensitivity to tar should select alternative treatments. The product’s efficacy does not rely on resistance mechanisms, because the action is physical (occlusion) and chemical (membrane disruption), rather than enzymatic detoxification.
In summary, tar‑based soap eradicates lice by suffocating the insects, compromising their cuticular integrity, disrupting cellular respiration, and impairing egg viability through a combination of occlusive, surfactant, and toxic effects. Re‑application after one week ensures complete eradication of the infestation.