Definition:
The Triple Response is a local cutaneous (skin) reaction
to a mild mechanical injury like a scratch or stroke on the skin.
It is used to study vascular and sensory nerve responses in the skin.
Stimulus:
- Firm
stroke with a blunt object (e.g. fingernail, stylus)
Three Components of the Triple
Response:
|
Response |
Time of Appearance |
Cause |
|
1. Red Line |
Within 10 seconds |
Capillary dilation due to histamine |
|
2. Flare |
~30 seconds |
Arteriolar dilation due to axon reflex |
|
3. Wheal |
1–2 minutes |
Increased capillary permeability → plasma leakage → edema |
1. Red Line
- Thin red
line at the site of stroke
- Appears in
10 seconds
- Due to dilation
of capillaries
- Mediated
by histamine
2. Flare
- Red area
spreading around the red line
- Appears in
30 seconds
- Due to dilation
of arterioles
- Caused by axon
reflex (neurogenic inflammation)
- Involves antidromic
nerve impulses → release of vasodilators like substance P
3. Wheal
- Swelling
at the site of stroke
- Appears in
1–2 minutes
- Due to increased
capillary permeability
- Caused by histamine
→ plasma leaks into tissues → edema
Mnemonic: RFW
- Red line → Capillary
dilation
- Flare → Arteriolar
dilation (axon reflex)
- Wheal → Water
leakage (edema)
Clinical Importance
- Demonstrates
histamine reaction → useful in allergy testing
- Indicates
integrity of cutaneous nerves and microcirculation
- Helps understand inflammatory responses
Tags
ANATOMY