Threshold for perception

It may be speculated that the actual application of a moisturizer satisfies an atavistic psychological need for physical contact, which is reinforced by the immediate physical effects of the moisturizer. It has been shown that the application of a moisturizer increases the tactile sensations in dry skin, both by lowering the threshold for perception and by allowing better point-discrimination.30 The use of a moisturizer therefore potentially enriches sensory perception. 

Quantitative somatosensory testing (QST) uses calibrated tools to assess the function of all the sensory modalities. The smaller caliber nerves are evaluated by measuring pain and temperature (hot and cold) thresholds, and larger caliber nerves are evaluated by measuring the thresholds for perception of vibration, joint position, and touch. This is done by touching the patients skin with stimuli of defined characteristics, such as a computer-controlled probe that can heat or cool to specific temperatures. The effectiveness of QST is limited because it requires subject cooperation and is inherently subjective, as it relies on the reported interpretation of sensory stimulation from the subject. This also influences reproducibility of this sensory test (Fink and Qaklander, 2006). 

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