Why does flea infestation cause itching? - briefly
Flea bites introduce saliva that contains anticoagulants and allergenic proteins, which stimulate histamine release and provoke a localized inflammatory response. The ensuing irritation of skin nerve endings produces the characteristic itching sensation.
Why does flea infestation cause itching? - in detail
Flea bites introduce saliva containing proteins that the immune system recognises as foreign. These proteins act as allergens, triggering mast cells to release histamine and other mediators. Histamine dilates blood vessels, increases permeability, and stimulates nerve endings, producing the characteristic redness, swelling, and intense sensation of itch.
The sequence of events can be outlined as follows:
- Saliva injection during feeding
- Antigen presentation to immune cells
- Activation of IgE antibodies specific to flea allergens
- Cross‑linking of IgE on mast cells
- Release of histamine, prostaglandins, and leukotrienes
- Vasodilation, edema, and activation of peripheral itch receptors
Repeated exposure amplifies the response; sensitised individuals develop larger wheals and more pronounced pruritus. Scratching damages the epidermis, allowing secondary bacterial infection, which further aggravates inflammation and prolongs discomfort.
Factors influencing severity include:
- Host species and genetic predisposition to allergic reactions
- Number of fleas and frequency of bites
- Condition of the skin, such as dryness or pre‑existing dermatitis
- Presence of concurrent irritants, like flea‑infested bedding or environmental allergens
Effective management requires eliminating the ectoparasite, using topical or systemic insecticides, and applying anti‑itch treatments that block histamine receptors or soothe the skin. Maintaining regular grooming and environmental hygiene reduces re‑infestation risk and limits the cycle of bite‑induced itching.