The gold standard for the diagnosis of allergic contact dermatitis is patch testing, during which allergens are affixed to the skin underneath tape and left for multiple days. A large area of clear skin is thus required for successful testing.

While the back is traditionally thought to be the ideal area for testing, the thighs may be more available or advantageous. This study seeks to randomize patients undergoing patch testing to have patches placed on the back or the thighs. The investigators seek to understand the benefits of testing on the legs versus the back in terms of patient experience as well as achieving a successful test. This study will measure patient experience using a survey administered to patients. Quality of testing will be assessed by study coordinators prior the removal of patches.

Background:

Patch testing for ACD is a rigorous process. While the patches are on the patient's skin, they must be careful not to perform movements that will cause the tape to detach, thus compromising the integrity of the test. The classical placement of patches is on the back due to: a) the large body surface area in which to place the patches, b) the generally flat surface which allows for adequate adhesion of the patches (as opposed to a more rounded body surface), and c) the difficulty for patients to manipulate the area, thus limiting patient interference with the testing site and ensuring the tape remains adhered. The primary disadvantages of placing patches on one's back are the physical limitations, e.g the inability to raise one's arms above shoulder level, bend, twist, or reach. This has both comfort and practical disadvantages as patients find it hard to drive, clothe, and perform their activities of daily living (ADLs). These limitations improve the quality of the testing, but it is reasonable to think that some discomfort could be prevented, as an element of the physical limitations result from pulling or tugging due to the copious amounts of tape applied to achieve complete occlusion. For patients who are parents or caregivers, or those who are unable to take off of work during the week, these limitations can prove to be an immense challenge. Breastfeeding mothers may be unable to comfortably feed their infants. Patients also report increased pain, sleeping difficulties, and worsening of rash during patch testing.

Thus, the investigators seek to investigate further patient comfort during patch testing to improve the patient experience. The thighs have been used in our clinic as a patch testing as an alternative to the back, either when the back has rash, tattoos, or too small an area for complete patch testing. Anecdotal evidence suggests that the thighs may provide a more pleasant patch testing experience with decreased restrictions in mobility. In our experience, no limitation has been seen in terms of the quality of the patches with placement on the thighs. To date, there has been little published literature regarding the ideal location of patch testing, either in respect to patient experience or quality of testing. One study has proposed alternatives to the tape used to adhere patches in an effort to improve comfort. Another study examined retrospective data to identify rates of symptoms during patch testing (pain, sleep difficulty, need for medication, site itching or itching elsewhere, and worsening rash) and their correlation with patch location. Various significant statistical associations were found, such as highest levels of pain with placement on the arms and increased need for medication and location on the chest. However, more information is needed comparing specifically the legs and the back, the two most commonly tested areas, in terms of patient comfort and quality of the test. Additionally, by obtaining a more holistic understanding of patient comfort, the investigators will be able to derive a more useful and clinically applicable answer as to whether the legs or back is preferable for testing location.

Sample Size:

Sample size will be determined using a pragmatic approach based on time constraints and size of recruitment pool. Because there exists no previously validated instrument to measure patient experience during patch testing (or something similar), the investigators will be developing our own survey. The survey will document important demographic information and assess patient experience during patch testing using agreements questions that will be compared between both groups. HealthPartners Center for Evaluation and Survey Research (CESR) will help to develop an effective instrument. 30 patients will be enrolled per treatment group. Between 10-20 patients are seen per week on average, and the investigators estimate that 20% will not meet inclusion criteria. Assuming that 50% of patients who meet enrollment criteria will agree to take part in the study, data collection will take between 8-15 weeks. 100% study follow through should be attainable, as it is very rare for patients who begin patch testing to be lost to follow-up.

Inclusion Criteria:

• Age 18 or older
• Undergoing patch testing at Park Nicollet Contact Dermatitis
• At least 90 patches applied at one time, representing comprehensive testing rather than limited testing with few patches that may skew results
• Both back and thighs adequate for patch testing (see exclusion criteria below)

Exclusion Criteria:

• Patient is 17 or younger
• Patient is pregnant or breastfeeding
• Specialized patch testing with low number of patches (less than 90)
• Rash that would preclude testing on thighs or back
• Large tattoos that would preclude testing on thighs or back
• Limited space on thighs or back due to body habitus
• Patient has specific needs necessitating use of the thighs or back (event, breastfeeding, etc.)