10 Days’ Minimum for Best ROAT Results

woman itching arm eczema atopic dermatitis
Woman scratching her arm.
The ideal duration for obtaining a positive repeated open application test (ROAT) for a topical product is investigated.

A study of the repeated open application test (ROAT) found that the test should be performed for at least 10 days to obtain robust results. These findings were published in Contact Dermatitis.

This multicenter prospective study was conducted by the Dermatology and Allergy Group (DAG) of the French Society of Dermatology. DAG members (N=21) prospectively collected data using a standardized questionnaire about all ROATs (N=328) performed from 2019 to 2020 to evaluate allergic contact dermatitis to cosmetics, topical medications, antiseptics, and other topical products. The ROAT standardized procedure was 2 daily applications of the test product on the forearm and front of the elbow fold in a 5×5 cm patch for 2 weeks. Patients were instructed to wash the product off as they would in a real-life scenario, corresponding with a 5-minute application time. The primary objective was to determine the optimal duration of ROAT for achieving a positive result.

The median number of ROATs recorded by dermatologists was 10.

ROATs investigated eczema of the face (27%), body (22%), and eyes (17%), among other regions. A ROAT was performed once per patient, except for 4 patients who implemented multiples tests.

The motivation for using a ROAT was to confirm a patch test result (52%), determine responsibility of suspected product before patch testing (27%), to exclude a product only slightly suspected (15%), and other reasons, such as to explore a cross allergy (n=20).

ROAT results were negative (77%), positive (18%), or doubtful (5%).

Among positive tests, 61% of the products had not previously been patch tested.

The median time to positivity was 3 (range, 1-10) days overall and among only positive tests without prior patch test, 2 days.

Among only ROATs for eyedrops (n=56), 70% were performed after a patch test. Eyedrop ROATs were positive (16%) at a median of 3 days and within 9 days.

The major limitation of this study was that a 2-week cut-off was used. It may be possible that some very late positive results were missed.

This study indicated to the researchers that a minimum of 10 days is needed to adequately perform a ROAT for exploring allergic contact dermatitis for topical medications and cosmetics. The investigators reported that reducing the ROAT to 1 week would potentially miss 8.5% of positive tests.


Amsler E, Assier H, Soria A, et al. What is the optimal duration for a ROAT? The experience of the French Dermatology and Allergology Group (DAG). Contact Dermatitis. Published online April 5, 2022. doi:10.1111/cod.14118