17th January 2024

Pathophysiology 

Not every individual exposed to the same allergen will go on to develop HP – indeed, most of those exposed will develop no clinical signs or symptoms post-exposure. In susceptible individuals, it has been proposed that in acute cases, exposure to the antigens in an allergen causes a type 3 hypersensitivity reaction, leading to IgG antibody production for that allergen’s antigens. Then, subsequent exposure to the same allergen results in a type 4 hypersensitivity reaction with increased CD4+ cell activity and cytokine release, leading to granuloma formation and other chronic pathological changes.

A genetic component to the disease has been suggested in a number of reports; however, no definite genetic risk factor appears to have been identified with a consistent link to HP development yet.