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Updated: Jun 12, 2026

Cheek Injection Model for Simultaneous Measurement of Pain and Itch-related Behaviors
Published on: September 27, 2019
Plant cysteine proteases that evoke itch activate protease-activated receptors
1Massachusetts General Hospital Cutaneous Biology Research Center, Charlestown, MA 02129, U.S.A.
Background:
Bromelain, ficin and papain are cysteine proteases from plants that produce itch upon injection into skin. Their mechanism of action has not been considered previously.
Objectives:
To determine the mechanism by which these proteases function.
Methods:
The ability of these proteases to activate protease-activated receptors was determined by ratiometric calcium imaging.
Results:
We show here that bromelain, ficin and papain activate protease-activated receptors 2 and 4.
Conclusions:
Bromelain, ficin and papain function as signalling molecules and activate protease-activated receptors. Activation of these receptors is the likely mechanism by which these proteases evoke itch.
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