A patient undergoing allergen immunotherapy experiences a localized skin reaction, despite gradually increasing allergen doses. Why does this localized reaction persist during desensitization?

💡 Explanation

Localized reactions persist because mast cells, already sensitized with IgE, degranulate and release histamine upon encountering the allergen, therefore causing inflammation and itching at the injection site, rather than systemic anaphylaxis, due to the localized nature of the exposure and limited allergen diffusion.

• Which outcome occurs when alternative pathway initiation escalates systemically?
• Why does enteric nervous system (ENS) activation during digestion cause increased intestinal motility in the small intestine rather than decreased motility?
• If a patient with presbyopia uses eye drops that paralyze the ciliary muscle, which consequence is most likely regarding their ability to focus?
• An elderly patient taking warfarin for atrial fibrillation experiences a fall, leading to a subdural hematoma. Why does warfarin increase the risk of hemorrhage in this case?
• If a patient's pulmonary capillary transit time falls below the equilibrium time for oxygen exchange, which consequence follows?
• If a viral infection triggers excessive cytokine production in lung tissue, which consequence most likely follows?