Do you often get rashes on your body? Sometimes it itches a lot, turns red, and peels... But you can't figure out what's causing it? Maybe you think it's because of the new bar of soap you bought, or maybe it's because of the new perfume you used. Maybe you wonder if it's because of some chemical you use at work. In times like these, we're going to talk about a special test that will help you find out exactly what's really "not working" on your skin.
Simply put, what is a patch test?
Patch Test is a type of skin allergy, that is, a test to detect an allergy. In particular, we use this to detect a condition called contact dermatitis . Now you may be wondering what 'contact dermatitis' is. Simply put, it means that after your skin comes into contact with something, your skin reacts to it and a rash develops within a few days. That means that for some people, the earlobes do not turn red immediately after wearing earrings, but only after two or three days. This test is used to detect things like that.
In this test, your doctor will place small patches on your skin (usually your back). Each patch contains a very small amount of the substance you suspect you are allergic to. The patches will be left on for about two days. The doctor will then remove the patches and check for any reactions. After that, the patches will be removed and the areas will be re-examined in about two days.
When should you do a patch test?
Your doctor, especially a dermatologist, may recommend this test for you if:
- If you frequently get rashes or eczema on your body, but you can't find a specific cause.
- If you suspect that something specific (for example, a cream you use) is causing this skin problem, you need to confirm it.
- If you think this skin problem is caused by a substance you use at work or in your hobbies (but don't know exactly what it is).
- If you are about to start a new job and you have to work with certain things in that job, you want to know in advance if you are allergic to those things.
Imagine you work in a salon. You often have to handle things like hair dye and shampoo. If your hands are constantly red, cracked, and itchy, this test can help you find out what chemical is causing it.
What types of allergies does this test detect?
This patch test can help you find out if your skin reacts to a lot of things that we can't even imagine. You can get a good idea of that by looking at the table below.
| Types of things that can cause allergies | Examples and simple explanation |
|---|---|
| Metals | Nickel, cobalt, gold. Many people get irritated and hurt when wearing 'imitation' earrings and necklaces, right? The reason for that is this metal called nickel. Also, sometimes some people are allergic to gold. |
| Fragrances | Fragrances found in perfumes, soaps, shampoos, body lotions, and cosmetics. Sometimes the cause of your acne could be the perfume you love to wear. |
| Preservatives | Chemicals used to preserve things like shampoo, conditioner, creams, and sunscreen. |
| What are the ingredients in hair dyes? | The chemicals in hair dyes and blackeners are the reason why some people get a swollen face after applying hair dye to their heads. |
| Topical medications | Some people may also be allergic to some antibiotic creams or steroid creams applied to the skin. |
| Rubber additives | Some people are allergic to things like rubber gloves and elastic bands in some clothes. |
| Plastics and resins | Things like epoxy or acrylates. These are used in the construction industry and dentistry. |
Okay, now let's see how to do this test...
This patch test is not something that can be completed in a day or two. It usually takes about a week. The reason is that the condition called 'contact dermatitis' that we talked about earlier takes several days to develop. So we have to be patient for a few days to see if there is a reaction.
This process usually goes like this:
First day (for example, Monday)
This is your first day of seeing the doctor. On that day, the doctor will apply the patches we mentioned earlier to your back (and sometimes your arms). These patches are applied securely with tape or something like a bandage so that they don't move. Then, they will mark the locations of the patches with a pen.
The next two days (Tuesday and Wednesday morning)
These two days are the hardest. You have to stay at home with these patches. During this time , you cannot let these patches get wet for any reason . That means you cannot shower or do anything that makes you sweat. If you get wet, the test results may be incorrect. So you have to be very careful during these two days.
Third day (for example, Wednesday)
You need to go see the doctor again. That day, he will remove the patches on your back and check for any redness or blistering. He will note these things down. After removing the patches, you can take a shower. But don't scrub your skin with soap or rub it. It's not a good idea to scratch or pick at those areas.
The fifth day (for example, Friday)
This is the last day. You need to go see the doctor again. He will check your skin again to see if there are any new reactions. This is because some allergies take 4-5 days to develop, which is why you are checked twice. Only after this test will you be told about your full result.
How should you prepare for the Patch Test?
There are a few things you should keep in mind before taking this test. Only by following these correctly can we get accurate results.
| Do's/Don'ts | Description and reason |
|---|---|
| Avoid sunlight. | Avoid exposing your back to direct sunlight for a week or two before the test. Sunburn can affect the results. |
| Stop using skin-soothing medications | If you are using any creams, such as steroids, on your back, stop using them a week before the test. These can reduce the skin reaction. |
| Don't apply moisturizer. | Do not apply any moisturizer or lotion to your back on the day of the test or during the test. |
| Let me know if you are pregnant. | Be sure to tell your doctor if you are pregnant or breastfeeding. Hormonal changes in the body during pregnancy can affect the results. |
| Allergy pills (Antihistamines) | Taking antihistamines such as paracetamol and piritan will not affect this test. So if you are taking them, you can continue to take them. But ask your doctor about this and make sure. |
| Inform about other medications | If you are taking steroid pills like prednisone or other medications that weaken the immune system, you should definitely tell your doctor. |
| Clothing | On the day of the patch application and for the week after the test, wear loose, easy-to-take -off clothing . A button-down shirt is best. Also, since the doctor will be marking with a pen, it's a good idea to wear dark clothing that won't stain. |
Things you should keep in mind throughout the week of the test
This is the most important part. You need to do these things exactly this whole week.
- Do not remove the patches for any reason or let them move. They should only be removed when your doctor tells you to.
- Avoid bending or twisting as this could dislodge the patch.
- Avoid sweating as much as possible. This means you should avoid exercising, going out in the sun, and staying in hot places for a few days.
- Even if the patch itches, do not scratch it .
- If a patch comes off or becomes loose, call your doctor immediately.
- Do not let the patch get wet under any circumstances. When bathing, do not apply water to your back, but only wipe the rest of your body with a washcloth. If you are washing your hair, bend forward and wash it in a sink.
Remember, 90% of the success of this test depends on you following these instructions exactly. Even if it is a little uncomfortable, you will have to be patient to get an accurate result.
Is there any risk in this?
This is generally a very safe test, but minor things can happen.
After the test, the skin may be slightly red and itchy where the patch was applied. Sometimes the skin in those areas may turn slightly white or black. These things will get better on their own in a few days or weeks.
However, very rarely , some people can have a severe allergic reaction, called anaphylaxis . This can usually happen within a few hours of applying the patch. So it's important to be aware of that as well.
When you need to talk to the doctor and go to a hospital immediately!
If you experience any discomfort during the test, it is very important to distinguish between normal and emergency situations.
| Inconvenience | What to do |
|---|---|
| General discomfort (call your doctor for advice) | |
| If you experience unbearable itching or pain in the areas where the patch was applied. | Call your doctor immediately and let him know. Don't do anything without asking him. |
| Emergency! (Go to the nearest hospital Emergency Department (ETU) immediately!) | |
| These are signs of a severe allergic reaction. Don't waste time and go to the nearest hospital's Emergency Department (ETU) immediately . |
If you are confirmed to be allergic to something, what do you do next?
After the last day of testing, the doctor will explain the results to you. If your skin has reacted to something (i.e., the result is positive), he will mark it according to its severity. For example, a (+) means a mild reaction. A (+++) means a very severe reaction. Things that have not reacted at all are marked as (-).
If you find out you're allergic to something, the next step is to avoid that substance and products that contain it. Your doctor can help you:
- It will give you a list of products that contain allergens.
- We provide you with a safe list of products to use.
- Sometimes, he'll even tell you about phone apps that let you scan the contents of items when you buy them.
This way, you can avoid allergies and live without skin problems.
Take-Home Message
- Patch testing is a very important test to detect allergies (contact dermatitis) that occur after something touches your skin.
- This test usually takes about a week. During this time, it is essential to follow instructions such as not getting the patch wet and not sweating.
- The accuracy of the test results depends entirely on how closely you follow the doctor's instructions.
- If it is confirmed that you are allergic to something, your doctor will give you guidance on how to avoid that substance.
- Although severe allergic reactions are very rare, remember to go to the Emergency Department (ETU) immediately if you experience symptoms such as difficulty breathing and facial swelling.
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