Chitin in food: ingestion safety

(People-specific data is limited; this page draws from human adult context.) Chitin is a linear polysaccharide of beta-(1->4)-linked N-acetylglucosamine, the second most abundant natural polymer after cellulose. It is a structural component of fungal cell walls and arthropod exoskeletons (insects, crustaceans, arachnids). In the context of fungal exposure, chitin is a potent modulator of innate immunity: it is recognized by multiple pattern recognition receptors including TLR2, Dectin-1, and mannose receptor, and activates the NLRP3 inflammasome. Chitin particle size determines immune response: large chitin fragments (>70 um) are inert; intermediate fragments (40-70 um) induce alternative macrophage activation (anti-inflammatory); small fragments (<40 um, typical of inhaled fungal debris) trigger NLRP3-dependent IL-1beta and IL-18 release, promoting Th2 inflammation and eosinophilia. This size-dependent immune activation is relevant to asthma pathogenesis — chitin exposure is associated with airway eosinophilia and mucus production. Chitinase enzymes (AMCase, chitotriosidase) are elevated in asthma and serve as biomarkers. Occupational exposure: shellfish processing workers show increased respiratory symptoms. Dietary chitin from mushrooms is generally well-tolerated and may have prebiotic properties.