Many agents are capable of causing comedo formation when applied to the skin. Comedones are plugged hair follicles and the comedogenicity in the rabbit ear assay also tend to produce comedones in human follicles.

In this study, we have used both the rabbit ear histological assay and subjective scoring assay to assess the comedogenic properties of Emu oil provided to us by Atlantis Laboratories.

Materials and methods:

1. Test chemicals. Emu oil (EO): 25% (EO25), 50% (EO50), 75% (EO75), and 100% (EO100) solution.
2. Animal treatment. The ears of male albino rabbits weighting 2-4kg were used in this study

Applications were made according to the following table


Rabbit No.	Left Ear	Right Ear
1-1		None
1-2#		None
1-3#		None
2-1#		EO25
2-2#		EO25
2-3#		EO25
3-1#	EO50	EO75
3-2#	EO50	EO75
3-3#	EO50	EO75
4-1#	EO100	None
4-2#	EO100	None
4-3#	EO100	None

3. Applications of test agents: Test agents were topically applied to the rabbit ear at the dosage of 0.1 ml daily for 5 days each week for three consecutive weeks. The site of application was a 2x2x2cm² area at the external ear canal notch.
4. Evaluation methods:
   1. Observational examination of the rabbit's ear was performed at the end of the second and third week of application by visual scoring of comedogenicity. The following scale was used for scoring.

   Grading Scale:

   0= No change

   1= Slight follicular hyperkeratosis in some follicles;

   2= Slight follicular hyperkeratosis;

   4= Moderate follicular hyperkeratosis with some plugging of follicles; and,

   5= Confluent plugging of follicles

   2. Histological examination was performed at the end of the test. A portion of the ear from the treated and control sites were biopsied. Vertical step sections were evaluated for histologic evidence of follicular plugging as defined by the American Academy of Dermatology Comedogenicity Consensus Group recommendations as follows:

   Grading Scale:

   0= No comedogenesis

   1= The presence of a relatively small amount of compact horny material occupying the infundibulum

   2= The presence of a moderate amount of compact horny material that widens the infundibulum and extends into the sebaceous ducts

   3= The presence of dense horny material that distends the follicle, resembling a human open comedo.

   Test Results

    

   1. EO25 treatment results
   Rabbit #/ear side	Observational Score	Histological Score
   2-1# / right	0.5	0
   2-2# / right	1.0	1.0
   2-3# / right	0.5	0
   Total score	2.0	1.0
   Average Score	0.7	0.3
   2. EO50 treatment results
   3-1# / left	0.5	0
   3-2# / left	1.0	0.5
   3-3# / left	0.5	1.0
   Total Score	2.0	1.5
   Average Score	0.7	0.5
   3. EO75 treatment results
   3-1# / right	0	0.5
   3-2# / right	0.5	1.0
   3-3# / right	0.5	1.0
   Total score	1.0	2.0
   Average Score	0.3	0.7
   4. EO100 treatment results
   4-1# / left	1.0	0
   4-2# / left	0.5	1.0
   4-3# / left	1.0	1.0
   Total score	2.5	2.0
   Average Score	0.8	0.7
   5. No application (Control)
   1-1# / right	0	0
   1-2# / right	0	0
   1-3# / right	0	0
   4-1# / right	0	0
   4-2# / right	0	0
   4-3# / right	0	0
   Total Score	0	0
   Average Score	0	0
   6. Summary of average scores
   Substance	Observational Score	Histological Score
   EO25	0.7	0.3
   EO50	0.7	0.5
   EO75	0.3	0.7
   EO100	0.8	0.7
   No Application	0	0

   
   

   Interpretation:
   An observational score of 1 or less is considered to indicate a substance that is unlikely to produce a comedogenic response during human use and is therefore considered to be a negative result.

   A histologic score of 1 of less is considered to indicate a substance that is unlikely to produce a comedogenic response during human use and is therefore considered to be a negative result.

5. Final Assessment:
   On the basis of observational and histologic testing for comedogenicity, the Emu oil used in this test, from 25% to 100%, is non-comedogenic.