In the context of allergic rhinitis, what is the primary response in the initial phase of an allergic reaction?

In the context of allergic rhinitis, the primary response in the initial phase of an allergic reaction is vasodilation and smooth muscle contraction. When an allergen is encountered, the immune system identifies it as a threat and initiates a response. The primary players in this response are immunoglobulin E (IgE) antibodies, which bind to allergens and trigger mast cells and basophils to release various mediators, including histamine.

Histamine release leads to vasodilation, which increases blood flow to the affected area and contributes to the characteristic symptoms of allergic rhinitis, such as nasal congestion and sneezing. Additionally, smooth muscle contraction can occur, particularly in the bronchi, which may contribute to symptoms like bronchospasm in more severe allergic reactions. Thus, this initial phase sets the stage for the subsequent inflammatory responses and symptomatology associated with allergic reactions.