Also called the Triple Response of Lewis
A "flush, flare, wheal reaction" with segmental/general rapid/delayed fading is produced when the skin is stroked on both sides of the spinal processes with a pointed instrument.
The response appears in about 15 seconds. This white line soon disappears followed by three reactions:
1- Red line.
2- Wheal.
3- Flare.
The red reaction appears at site of stimulus within 10 second due to capillary dilation, this is followed by local swelling (edema) around injury within few minutes due to increase permeability of the capillaries and post capillary venules with extravasation of fluid. The redness spreading out from the injury (flare) is due to arteriolar dilation. This three response (red, wheal and flare reactions) is called triple response.
Empirical conclusions are drawn about somatic dysfunctions (SD) and vegetative changes.
The current hypothesis of the axon reflex postulates the existence of syndrome axonal transport mechanisms and the local release of mediators.
These essential mediators of the "flush, flare and wheal reaction" according to Lewis is histamine.
There are also complex interactions of the Nervous, Immune, and Neuroendocrine System including substance P, CGRP, bradykinin etc.
The above-mentioned mechanisms lead to vasodilatation, and in chronic cases a dominance of the sympathetic vasoconstrictor activity is postulated, leading to a rapid fading of the skin reactivity.
In the segment where there is an abnormal reaction, the osteopath has to examine the different tomes of the segment for dysfunction.