Tea tree oil reduces histamine-induced skin inflammation.
BACKGROUND
Tea tree oil is the essential oil steam-distilled from Melaleuca alternifolia, an Australian native plant. In recent years it has become increasingly popular as an antimicrobial for the treatment of conditions such as tinea pedis and acne.


OBJECTIVE
To investigate the anti-inflammatory properties of tea tree oil on histamine-induced weal and flare.


METHODS
Twenty-seven volunteers were injected intradermally in each forearm (study and control assigned on an alternating basis) with histamine diphosphate (5 microg in 50 microL). Flare and weal diameters and double skin thickness were measured every 10 min for 1 h to calculate flare area and weal volume. At 20 min, 25 microL of 100% tea tree oil was applied topically to the study forearm of 21 volunteers. For six volunteers, 25 microL paraffin oil was applied instead of tea tree oil.


RESULTS
Application of liquid paraffin had no significant effect on histamine-induced weal and flare. There was also no difference in mean flare area between control arms and those on which tea tree oil was applied. However, mean weal volume significantly decreased after tea tree oil application (10 min after tea tree oil application, P = 0.0004, Mann-Whitney U-test).


CONCLUSIONS
This is the first study to show experimentally that tea tree oil can reduce histamine-induced skin inflammation.
Koh
K J
KJ
Department of Dermatology, Flinders Medical Centre, Bedford Park, South Australia, Australia.
Pearce
A L
AL
Marshman
G
G
Finlay-Jones
J J
JJ
Hart
P H
PH
D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use*; D016022:Case-Control Studies; D003876:Dermatitis, Atopic / Q000188:drug therapy* / Q000209:etiology / Q000473:pathology; D005260:Female; D006632:Histamine / Q000031:analogs & derivatives*; D006801:Humans; D007271:Injections, Intradermal; D008297:Male; D008875:Middle Aged; D008517:Phytotherapy; D020947:Tea Tree Oil / Q000627:therapeutic use*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D020947:Tea Tree Oil; D006632:Histamine; C027556:histamine phosphate