Everything You Need to Know About Patch Testing
Everything You Need to Know About Patch Testing
This content has been reviewed and approved for quality and accuracy by James O'Loan (GPhC: 2084549)
When it comes to the skin, there is a wide number of substances that can cause negative effects on it. Effects on the skin can be caused by either an allergic reaction or an irritant in the product. If you are not sure as to what is causing any skin reaction, then you may do patch testing on the skin to determine what, if anything, is causing a reaction.
What is patch testing?
Patch testing is a form of testing on the skin that is conducted by a specialist, either a dermatologist doctor or nurse. The test is to determine whether the skin condition that you currently have is the result of an allergic reaction. This is what is known as a contact allergy. Patch testing is conducted when you have a skin condition such as eczema/dermatitis that helps to determine if the condition is caused by an allergy.
Who is patch testing suitable for?
Patch testing can be conducted on anyone who may have a skin condition, such as allergic contact dermatitis. Age wise, testing can be done from a very young age. For young children, it is best to be done when they have come into contact with a range of substances and materials, such as rubber, metals, plastics, and fragrances. Patch testing may not be done of people who are pregnant, breastfeeding, have bad eczema on the back, have a suntan, been on a sunbed in the last 2 weeks, are using a medium or high amount of steroids. If you feel any of these apply to you, rearrange the appointment.
What substances are tested in patch testing?
In most tests, there are around 40 different substances that are tested on the skin to find out if it causes an allergic reaction. Substances that can be tested include:
- Rubber Latex
- Cosmetic products
If a particular substance is thought to trigger the skin, then that will also be tested.
The first time you go to an appointment regarding patch testing, there is a number of things that you should take:
- Any medication that you are currently taking
- Any ointments and creams that you are using, including both prescribed and purchased treatments
- Products that you use can be brought if you think that they may be causing or contributing to the skin condition. This can include toiletries, cosmetics, or hair products. Anything you place on the skin, take both the product and the packaging. For household items, such as cleansers, washing powder, or fabric softeners, only bring the packaging with the ingredients on them. If you are told to bring any product, then ensure that you do so.
- Products from work can also be brought in for patch testing as well. If you think a substance from your workplace may be affecting your skin, then bring in the Health and Safety Data sheet (COSHH sheet) and also the product itself, if it is necessary to do so.
If you are unsure about what you should take, then speak to the doctor before going to the appointment.
How is patch testing conducted?
The whole patch testing process is done in three appointments. The first appointment consists of the substances being applied to the skin using special small discs which are about 1cm in diameter. These are attached to the skin using hypoallergenic tape. The discs are placed onto the back, where they are identified using ink markings. Sometimes, the thighs or arms may be used for testing. The discs when placed will likely cause itching, which is normal. Do not scratch the discs when placed onto the skin. This first appointment will last for up to 2 hours in total.
All of the substances placed using discs will remain where they are until the second appointment. This is where they are removed and any allergic reactions are noted down. Additional patches can also be added at this stage. Any marking ink will stay on the skin for 2 more days until the third appointment.
At the third appointment, the areas of testing will be examined for any reactions which will then be discussed with you. The results will help the doctor when it comes to determining what is causing the skin condition. Sometimes a reaction can take up to 2 weeks before it appears. If a reaction appears late, then contact a doctor as soon as possible. Some substances can stain the skin. This is normal and will wash off. Also, do not expose the back to the sun or any artificial sunlight while testing.
Can I have a bath or shower with the patch tests on?
With the tests on the back, it is recommended that you do not have a bath or shower. The tests need to stay dry.
What clothes are suitable to wear when having patch tests?
Any clothing that you value, or anything pale coloured, should not be worn as they could be damaged by the marker ink used for the patch testing. It is also recommended that you wear clothing that can unbutton from the front, such as a shirt, as it is easier to remove than something that goes over the head.
Can I do exercise while having patch testing?
When patch testing, avoid doing any sport, exercise, or heavy lifting. This is because sweating will cause the patches to come off. If a patch does begin to peel off, tape it down using Micropore tape. If a patch comes off completely, note the time and date it came off.
Are there any side effects that could occur when patch testing?
Side effects from the patch testing are rare, but it can happen. Potential side effects from patch testing include:
- Skin reddening and itching at the places where substances where applied. This will cause a positive result in the test. This reaction should disappear after a few days though.
- A persistent reaction, which can take up to a month to disappear.
- An eczema flare-up that may be a previous case that has returned.
- Skin pigment change may occur where the patches were. They can be temporary or in rarer cases, permanent.
- An infection which would require treatment, like antibiotics
- Scarring on the skin
- An allergy which occurs as a result of testing one or more of the substances.
If you notice any side effect, speak to the doctor.
How are the results of patch testing determined?
All patch testing results are stored in a database, though they are anonymised. This allows for the testing to be standardised and for sharing of the data for research. The results for patch testing is recorded after both the second and third appointments. The results are recorded in the following way:
- Negative (-)
- Irritant Reaction (IR)
- Equivocal/Uncertain (+/-)
- Weak Positive (+)
- Strong Positive (++)
- Extreme Positive (+++)
Your results will be explained to you and you can get advice on what treatments, if any, that you can use in the event of having a skin condition.