Why does the scabies mite cause itching? - briefly
The mite penetrates the skin and releases saliva containing proteins that provoke an immune response, causing inflammation and histamine release that produces intense itching. This hypersensitivity to mite antigens escalates with continued exposure, amplifying the pruritic cycle.
Why does the scabies mite cause itching? - in detail
The itch associated with scabies results from a complex interaction between the parasite’s activity and the host’s immune system. Female mites excavate tunnels within the stratum corneum to deposit eggs. This mechanical disruption damages keratinocytes, exposing nerve endings and triggering immediate sensory signals.
During feeding, mites inject saliva that contains proteolytic enzymes, cysteine proteases, and other antigens. These molecules penetrate the epidermal barrier, where they are recognized as foreign by antigen‑presenting cells. The subsequent activation of T‑lymphocytes leads to a delayed‑type hypersensitivity reaction (type IV). Cytokines such as interleukin‑1β, interleukin‑6, and tumor necrosis factor‑α are released, promoting inflammation and sensitizing cutaneous nerve fibers.
Mite feces and shed cuticle fragments remain within the burrows. Their protein components act as allergens that stimulate IgE production. Binding of IgE to mast cells induces degranulation, releasing histamine, tryptase, and other mediators. Histamine directly provokes pruritus by activating H1 receptors on peripheral nerves.
The combined effect of:
- Physical irritation from tunnel formation,
- Enzymatic damage caused by salivary secretions,
- Immune activation against mite‑derived antigens,
- Mast‑cell‑mediated histamine release,
produces the characteristic intense itching. The reaction typically intensifies after two to four weeks, reflecting the time required for sensitization. Continuous scratching further damages the skin, creating secondary lesions that perpetuate the inflammatory cycle.