Human Repeated Insult Patch Test

The Human Repeated Insult Patch Test is a 6 week study that is the industry standard for determining the potential of a test material to induce sensitization in humans after repeated exposure. Although it is not the main objective, it may also provide information on the potential of the material to elicit an irritant reaction under the conditions of the study. The material being tested may be an individual component intended to be used in a cosmetic, toiletry, drug, device or personal care product or may be the completed product. Eurofins CRL (ECRL) offers “shared panels”, where your product will be tested on a panel with other Sponsors’ products, and “exclusive panels” on which only your products will be tested. You may select the number of subjects you would like tested, either 50, 100, 200, or more, however ECRL recommends testing at least 100 subjects.


ECRL uses a 24 hour exposure protocol. The provided test product is applied to occlusive or semi-occlusive patches, depending on the product type and end-use of the product. The patch is applied to the upper back of test subjects and is allowed to remain in direct skin contact for 24 hours, at which time the subjects remove the patches. Patch RoomSubjects return 24 hours after patch removal for evaluation of the site and re-patching. This procedure is repeated 9 times over an approximate 3 week period, with patch applications and scoring of sites generally being done on Mondays, Wednesdays, and Fridays and patch removal being done by subjects on Tuesdays, Thursdays and Saturdays. This is known as the Induction Phase of the study.

After a rest period of approximately 14 days, with no test product exposure, subjects return for the Challenge Phase. Test products are applied under the same patch type to a virgin site on the lower backs of the subjects and are removed by ECRL staff approximately 24 hours later. The sites are evaluated and intensity of reactions scored 24 hours (immediately after patch removal), 48 hours and 72 hours after patch application, as well as at 96 hours if a reaction persists.

Interpretation & Reporting of Results

Interpretation of results should not be made prior to the end of the study, as “the whole picture” needs to be evaluated in order to make an accurate conclusion. In general, minimal, transient reactions consisting of mild erythema, occurring during the Induction or Challenge Phases, are indicative of irritation, and unless observed in more than a few subjects, are not clinically significant. Induced sensitization reactions may occur toward the end of the Induction Phase and/or only during the Challenge Phase and would include a more intense level of erythema (moderate to severe) with obvious edema at or beyond the patch site, and are usually accompanied by a subjective complaint of itching. Unaudited Topline Results (preliminary conclusion) will be sent to you within 1 week of study completion, followed by a complete Final Report 4 to 6 weeks after study completion.

Scheduling a RIPT

Generally, Eurofins CRL has a HRIPT panel starting every week. To reserve a spot for your test sample(s), please contact one of our Client Services Representatives via email: