18 Capsaicin

Learning Objectives

Know how Capsaicin causes pain.

Be able to describe how Capsaicin treats pain.

Capsaicin is the oil-soluble chemical that is found in hot chili peppers (it’s what makes them hot!!).


Red and Green Chili peppers are sitting in a pile
Fig. 2.9.1. Chili Peppers. Chilies and other spicy peppers like these contain the chemical capsaicin. This chemical causes the pain we feel after eating spicy foods (and is the reason why it lingers for so long!). (Credit: John Lambeth. Provided by: Pexels. License: CC-BY)

In the body, there are two distinct types of somatosensory signals transduced by free nerve endings: pain and temperature. These modalities rely on thermoreceptors and nociceptors to convert temperature and pain stimuli. The perception of potentially harmful stimuli, called nociception, involves skin receptors detecting heat, cold, intense force, and chemical insults.

Most nociceptors respond to various forms of stimuli such as noxious mechanical pressure, extreme temperatures, and chemicals. This is what gives them the name polymodal. When you consume capsaicin, the molecules of capsaicin activate polymodal nociceptors responsive to heat and capsaicin, inducing a sense of pain.

The dynamics of capsaicin are odd in the way that the molecule remains bound for an extended amount of time. This property leads to a decrease in the nociceptor’s ability to respond to other stimuli. This diminishes the ability to evoke pain receptions. We have taken advantage of that by making topical analgesics using capsaicin as one of the main ingredients. One popular example of this is Icy Hot™.



To learn more, watch this Ted Talk linked here and included below.



OpenStax, Anatomy and Physiology Chapter 14.1 Sensory Perception
Provided by: Rice University.
Access for free at
License: CC-BY 4.0
Adapted by: Andrew Barnard and Grace Billadeau


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Introduction to Sensation and Perception Copyright © 2022 by Students of PSY 3031 and Edited by Dr. Cheryl Olman is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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