Allergic inflammation immediate allergic reaction or as a Type I allergic reaction. The reaction is caused by the release of histamine and mast cell granule proteins by a process called degranulation, as well as the production of leukotrienes, prostaglandins and cytokines, by mast cells following the cross-linking of allergen specific IgE molecules bound to mast cell FcεRI receptors. These mediators affect nerve cells causing itching, smooth muscle cells causing contraction (leading to the airway narrowing seen in allergic asthma), goblet cells causing mucus production, and endothelial cells causing vasodilatation and edema. The late phase of a Type 1 reaction (which develops 8–12
Juniperus virginiana female), 'Goldspire' (narrow conical with yellow foliage), and 'Kobold' (dwarf). Some cultivars previously listed under this species, notably 'Skyrocket', are actually cultivars of "J. scopulorum". In the Missouri, Oklahoma and Arkansas Ozarks, eastern juniper is commonly used as a Christmas tree. The pollen is a known allergen, although not as potent as that of the related "Juniperus ashei" (Ashe juniper), which sheds pollen a month earlier. People allergic to one are usually allergic to both. "J. virginiana" sheds pollen as early as late winter and through early spring. Consequently, what begins as an allergy to Ashe juniper in the winter