sensitization

Sensitization is a process by which a biological system becomes more responsive to a stimulus after prior exposure. The term is used across disciplines, including immunology, neuroscience, and pharmacology, and can involve immune reactions, neural plasticity, or altered drug responsivity.

In immunology, sensitization refers to the development of an immune memory to an antigen, typically allergen-specific IgE. After an initial exposure, the immune system produces IgE that binds to mast cells and basophils; later exposures cause cross-linking of surface IgE and release of mediators such as histamine, producing allergic symptoms. Primary sensitization and elicitation describe the stages of this process.

In neuroscience and pain science, sensitization denotes an increased response of neurons to stimulation, often after repeated or intense stimuli. Central sensitization, a key concept in chronic pain, involves amplified signaling in the spinal cord and brain, leading to hyperalgesia (increased pain from noxious stimuli) and allodynia (pain from normally non-painful stimuli). Mechanisms include synaptic plasticity, receptor changes, and glial signaling.

In pharmacology and toxicology, sensitization describes an enhanced effect of a drug after repeated exposure (as opposed to tolerance). This can involve changes in receptor density and signaling pathways and is discussed in contexts such as stimulant drugs and environmental chemical sensitizers.