Patch testing is a diagnostic procedure used in dermatology to identify substances (allergens) that cause contact allergic dermatitis (Type IV delayed hypersensitivity).
It involves applying small amounts of potential allergens to the skin (usually the back), under occlusion, and observing for reactions over several days.
Keep in mind, it does not detect immediate (Type I) reactions.
As the inks we use in both tattooing and permanent make-up may contain metals, preservatives and other chemicals, it's a good idea to patch test your clients.
The jury's out on whether it's actually reliable for tattooing and pmu as ink allergies can arise weeks, months or even years after the process.
This can be the result of sun or intense light exposure, changes in the skin, or things like new ointments or fragrances being used. It's extremely difficult to determine the actual reason we
develop delayed allergies to inks.
That being said, some organisations, health services and local government councils recommend it.
If you're required by regulations or legislation to patch test clients then you should patch test your clients according to their requirments.
It's also a good idea to speak to your insurance company (studio and personal indemnity insurance) as to whether they recommend/require it, regardless of what legislations says, just to make sure you have all your bases covered.
Even if not required by your regulations to patch test, there's always 'Duty of care' which can be brought up in a legal dispute. In this instance having a record of a completed patch test can't hurt your defense.
Duty of care is a legal and moral obligation to ensure the safety and well-being of your clients. It requires individuals and organizations to take reasonable steps to prevent foreseeable harm.
If you're patch testinging clients make sure you're doing it in accordance to the requirments set out by your local council or representative professional body.
Patch testing requirments may vary from city, state or country.
We've outlined a traditional process (in the UK) for patch testing below, this is an example of patch testing only, ensure you follow what's required from you by your local laws.
Provide your client with written information (or a digital version) so they undertand the process.
Ensure your client fills in a patch test consent form and understands the process, what will be expected of them and any risks invovled.
Ensure you're wearing gloves throughout the process (preferably nitrile), if you're using latex gloves ensure the client has no existing allergy to latex.
Use your preferred or mandated patch test process to apply each ink and make notes on location.
Take photos of the patch tested area.
Provide the client with a verbal and written (or digital) information sheet on how to care for the area and what to do if they have a reaction.
Book the client a follow up appointment or advise them on how to report results (send in photos etc..)
Note : Sukiru allows you to create a patch test, note the site (location), inks used, take photos and annotate them with the inks used. This provides an easy way to note what inks were used in which location and position, viewable in an image and can be included in a patch test report.
Depending on your process you may take a single reading or more (either in person or via a submitted high quality image of the site from the client). Generally a reading at 48 hours and 7 days is suffice.
A reading after 7 days might show delayed reactions eg to some metals.
Grade and record the result of each ink used.
Take photos of the results if possible.
Note :
There are a number of gradings for patch test results.
Sukiru uses a subset of these and narrows them down to 5 different results, Dermatologists may use a wider range of results.
Possible gradings :
If all results are Negative or both you and the client are happy with the results you may decide to go ahead with the appointment.
If any of the results were questionable or showed a possible positive reaction, you may want to wait awhile longer for results or do another patch test. Alternatively exclude the inks that showed concern from your palette for this session.
You may also want to consider asking your client to refer to a dermatologist. You can provide a report from Sukiru with ink details if neccessary.
Doubtful reactions are faint red spots without much swelling; these may or may not mean anything and often need further checking (e.g., repeat testing).
Irritant reactions are not allergies; your skin just didn't like the substance in a non-immune way.
A positive patch test will usually look like a small, red, itchy spot (or raised/bumpy area) under where the patch was applied.
Mild ones feel slightly firm and may itch.
Stronger ones can have small blisters and feel more swollen.
Very strong reactions can blister significantly and take longer to settle.
Ensure you take photos of all results.
Reactions occur if the client has an allergy to a substance in the ink, the redness/inflamation usually fade in a few days, sometimes weeks.
References
https://www.guysandstthomas.nhs.uk/our-services/skin-allergies/appointments
https://www.ouh.nhs.uk/media/vppav4m5/102369patch.pdf
https://my.clevelandclinic.org/health/diagnostics/patch-test
https://www.bad.org.uk/pils/patch-testing
https://cdn.bad.org.uk/uploads/2021/12/16103836/Patch-testing-PIL-July-2024-1.pdf
https://www.chemotechnique.se/patch-testing/interpretation-/
https://www.dermareading.co.uk/patch-testing
https://bdng.org.uk/wp-content/uploads/2017/02/FINAL130117.pdf