Autonomic and skin digital biomarkers
Signals read at the surface of the skin, shaped by ambient conditions as much as by the physiology underneath them.
.png)
The autonomic nervous system regulates processes people do not consciously control, including heart rate variability, sweating, skin temperature and vascular tone. Because several of those processes surface at the skin, they can be sensed by devices worn against it, which is why this domain exists as a distinct category rather than being distributed among the organ systems it affects.
The measures collected here include electrodermal activity, peripheral and core adjacent skin temperature, and the skin level signals used in dermatological research such as nocturnal scratching. What unites them is that they are proximal signals: they reflect underlying physiology indirectly, through a pathway that is influenced by ambient conditions as much as by the state of interest.
That indirectness is the defining constraint. Skin temperature at the wrist follows the room as well as the body. Electrodermal activity responds to heat and movement as well as to arousal. These are not flaws to be engineered away but properties of the measurement, and studies that account for them explicitly, by recording ambient conditions and analysing within person change rather than absolute values, get considerably more out of these signals than studies that do not.
Autonomic and skin measures in this library
How these measures are used
The most established use is nocturnal scratch measurement in dermatology trials. Itch is the symptom that matters most to people with inflammatory skin disease, it is severe at night, and it is poorly captured by a daytime questionnaire asking someone to recall how much they scratched while asleep. Wrist worn accelerometry addresses that gap directly, which is why this application has clearer traction than most in the domain.
Skin temperature is used as a physiological covariate, in fever and infection detection research, and in menstrual cycle work where a small nocturnal shift carries information. Electrodermal activity is used in arousal research and as an input to seizure detection algorithms, where it contributes alongside movement rather than standing alone.
Across these uses, the pattern is consistent: autonomic and skin measures are rarely the sole endpoint. They contribute additional physiological dimensions to a study whose primary outcome sits elsewhere.
What the evidence supports today
Evidence in this domain is early, and the honest summary is that these are promising signals rather than established endpoints. Nocturnal scratch measurement has the strongest position, with validation against video reference and use in dermatology trials, though scratch algorithms still vary between research groups.
Skin temperature from wrist wearables tracks relative change within a person reasonably well and is not an accurate estimate of core body temperature, a distinction that consumer products often blur. Its usefulness comes from detecting deviation from an individual baseline rather than from any absolute reading.
Electrodermal activity has decades of laboratory research behind it and much less evidence from free living conditions, where movement, ambient temperature and electrode contact all introduce variation that a laboratory setting controls. No measure in this category currently holds a regulatory qualification as a clinical trial endpoint, and studies using them should treat them as exploratory unless a specific application justifies otherwise.
Common questions
Can a wearable measure body temperature?
It measures skin temperature at the point of contact, which is influenced by ambient conditions and blood flow as well as by core temperature. That makes it useful for detecting change relative to a person's own baseline, and unreliable as an absolute reading. It is not equivalent to a clinical thermometer.
What is electrodermal activity?
A measure of small changes in the electrical conductance of the skin, driven mainly by sweat gland activity under sympathetic nervous system control. It rises with physiological arousal, but also with heat, exercise and movement, so interpreting it as an emotional signal requires controlling for those alternatives.
How is scratching measured objectively?
With wrist worn accelerometers, usually at night, running an algorithm that distinguishes the characteristic movement pattern of scratching from other hand movement. It is used in dermatology trials because it captures a symptom that occurs during sleep, which participants cannot reliably report the next morning.
Why are these measures kept separate from cardiovascular measures?
Because they reflect autonomic regulation observed at the skin rather than cardiac function directly. Some measures, notably heart rate variability, sit in both categories legitimately, since they are cardiac signals used as autonomic indicators. Grouping the skin level signals together makes the shared measurement constraints, particularly sensitivity to ambient conditions, easier to reason about.
Run a study on these measures
WeGuide captures wearable data and patient reported outcomes in one platform, from screening through to analysis.
