Facial Sting Study

The facial sting test is used to determine the potential of a test material to cause a stinging sensation on the skin of subjects who are known “lactic acid stingers”. A positive stinging response to lactic acid is sometimes used to identify a panel of “sensitive-skin” subjects, although very frequently, there is no visible erythema associated with the stinging response. The Facial Sting Study requires pre-screening of new subjects or re-screening of previously identified lactic acid stingers within one year of initiating a study. The one-day study can be conducted on 10 subjects per day. Normally, ten to twenty subjects are enrolled in a study.


A single unit of the test product will be provided by the Sponsor in a quantity of no less than 30ml. Potential subjects, presenting with Fitzpatrick skin types I – IV, will be pre-screened using a 10% lactic acid solution and saline. Subjects who detect a stinging sensation from the lactic acid of greater than mild on a pre-determined numeric scale and less than mild to the saline will be identified as “lactic acid stingers” and will be eligible to participate in a Facial Sting Study for up to one year. The provided test product will then be tested against saline. Assignment of test product or saline to either side of the face of each subject will be determined by a computer-generated randomization schedule. After washing the face with a non-moisturizing soap and holding a moistened, heated towel to the right side of the face for 2 minutes, approximately 500 ml of the test product will be applied to the suborbital area, malar area and nasolabial fold using a cotton-tipped swab. Subjects will then rate the degree of stinging on any of the areas of application at 1 minute, 2.5 minutes, 5 minutes and 8 minutes after application. At the end of the 8 minute period, study staff will observe the areas of application for erythema and the subject will rinse the face with clear water. Following a 15-minute rest period the procedure will be repeated on the left side of the face, with the alternate test material. Stinging intensity scores from the test product will be compared to the lactic acid stinging score obtained during the screening test for each subject.

Interpretation and Reporting of Results

Discomfort scores obtained during the testing phase will be statistically compared to those obtained from the saline during the study as well as to scores for the lactic acid obtained during the screening test of individual subjects.

At the request of the Sponsor, topline results may be provided verbally or in writing after statistical analysis has been performed. A written final report follows shortly thereafter.

Scheduling Facial Sting Study

To schedule, please contact your Client Services representative at 732-981-1616 or contact Diane Dolgan at 732-393-5754 or by e-mail: diane.dolgan@crlresearchlabs.com.