Ethnic differences in pain, itch and thermal detection in response to topical capsaicin: African Americans display a notably limited hyperalgesia and neurogenic inflammation.
BACKGROUND
Topical application of capsaicin commonly produces burning, stinging and itching as well as hyperalgesia to heat stimuli via activation of transient receptor potential vanilloid subtype 1.


OBJECTIVE
To investigate whether there are differences in sensory response and neurogenic inflammation to topical capsaicin in four different ethnic populations with different skin types.


METHODS
The study was performed in 40 healthy subjects consisting of 10 African Americans, 10 East Asians, 10 Hispanics and 10 Caucasians. Warmth sensation and heat pain detection thresholds, as well as pain intensity, were measured before and after application of capsaicin or placebo on forearms along with skin blood flow and the extent of the flare reaction.


RESULTS
In African Americans the heat pain detection threshold, pain intensity and skin blood flow did not change significantly after capsaicin application, while in the other three ethnic groups a significant change occurred characterized by hyperalgesia and vasodilatation. The postcapsaicin warmth sensation threshold increased in African Americans and decreased in Hispanics, the latter also uniquely experiencing postcapsaicin itch.


CONCLUSIONS
Our observations indicate that African Americans display a limited hypersensitivity following topical capsaicin, compared with the three other ethnic groups.
Wang
H
H
Department of Dermatology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
Papoiu
A D P
AD
Coghill
R C
RC
Patel
T
T
Wang
N
N
Yosipovitch
G
G
D000328:Adult; D001741:Black or African American; D044466:Asian People; D002211:Capsaicin; D005260:Female; D006630:Hispanic or Latino; D006358:Hot Temperature; D006801:Humans; D006930:Hyperalgesia / Q000139:chemically induced / Q000208:ethnology*; D008297:Male; D008875:Middle Aged; D020078:Neurogenic Inflammation / Q000139:chemically induced / Q000208:ethnology*; D010146:Pain / Q000208:ethnology*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000208:ethnology; D011537:Pruritus / Q000139:chemically induced / Q000208:ethnology*; D012039:Regional Blood Flow / Q000187:drug effects; D012684:Sensory Thresholds / Q000187:drug effects; D012867:Skin / Q000098:blood supply; D044465:White People; D055815:Young Adult
D002211:Capsaicin