Patch testing
Information for patients from Dermatology
This leaflet explains the following.
What patch testing is.
What you will be tested to.
How to prepare for your appointments.
What will happen at your appointments.
What the possible side effects are, and what reactions you may have.
We hope this leaflet answers some of the questions you may have. If you have any further questions or concerns, please speak to a member of your healthcare team.
What is patch testing?
Patch testing can help your doctor determine whether your skin condition is caused by an allergy to substances. These substances can come into contact with your skin either at home, at work, or during leisure activities.
To what will I be tested?
At the Patch Test clinic, we will test you to around 50 standard substances commonly in contact with the skin. For example:
rubber
chemicals
metals
perfumes
plants, and
also additional substances depending on your skin problem.
We may also test you to other relevant substances, including those found at your work or home.
What should I bring to the Patch Test clinic?
If you are an adult, your first appointment will be a telephone appointment. If the appointment is for your child, there will be no telephone appointment. A doctor will see them at their first appointment.
At this appointment your doctor will discuss the following with you.
Any prescribed drugs you are taking.
Ointments and creams you use, including over-the-counter creams.
Your own products, including substances you use at home which you think you might be allergic to. These include toiletries, cosmetics, nail polish, perfumes, and hair care products.
Work chemicals, if you think that substances at work may be aggravating or causing your rash.
Your doctor will let you know if you need to bring anything with you for testing.
What does patch testing involve?
You will need to visit the hospital twice.
On the first visit you will meet with the patch testing nurse. They will apply the substances to be tested in special patches to your back and the sites marked with ink. Each patch contains 10 allergens. Please allow up to 1 hour for this visit.
These patches will remain in place for 2 days. After 2 days you remove them and mark with a special pen, as shown to you by the patch testing nurse. You then need to take a photo of your back to bring along to your second visit.
At your second visit (on day 4 or 5) your back will be checked. You will discuss any reactions with your doctor. Please allow 30 minutes for this visit.
What reactions could I have?
It is possible that your patch tests will be negative. This is helpful since as far as we can, we have eliminated contact allergy as a cause of your skin problem.
Positive reactions become red and itchy at the test site. This usually becomes obvious by your day 4 reading, but it can take longer.
If you develop a late reaction, please contact the clinic on telephone 01227 783167 or 01843 235084.
Sometimes substances may stain your skin; this is normal.
Are there any reasons why I cannot have a patch test?
We may not patch test you if you:
are pregnant or breastfeeding;
have extensive eczema on your back;
have had sun exposure or used a sun bed over the past 2 weeks; or
are on a moderate or high dose of steroids.
If any of these apply to you, phone the clinic to rearrange your appointment.
What should I avoid before and during patch testing?
Try to avoid antihistamines for 48 hours before your first appointment.
Do not
Get your back wet during the tests; wash with a flannel.
Wear your best clothes, as the marker ink may stain.
Expose your back to the sun during patch testing.
Do
Avoid sport or heavy physical work during the week of your tests.
Wear an old bra or t-shirt for the week of your tests. Wear a t-shirt or vest to sleep, to protect the tests.
Reinforce with tape if a patch peels off. If a whole patch comes loose, remove the patch and note the time and date.
If you have any concerns, contact us on telephone 01227 783167.
What are the possible side effects?
Side effects are rare, but can include the following.
Skin reddening and itching from positive test results. This usually disappears after a few days.
Persistent reaction. Some positive test reactions (for example to gold) may persist for up to 1 month.
A positive patch test may result in a flare-up of existing or previous eczema.
An increase or decrease in pigment may be seen at the site of the patch tests.
Infection or scarring; these are rare. Rare means it affects between 1 in 10,000 and 1 in 1,000 people.
Sometimes you may become allergic to one of the substances used during patch testing. In practice this does not seem to cause a long-term problem. This can happen to around 1 in 500 patients.
Useful web sites
[Web sites last accessed 10 March 2026]
What if I have any questions or concerns?
If you have any concerns or need further information about your condition or the tests, please contact one of the following.
Dermatology, Kent and Canterbury Hospital, Canterbury
Telephone: 01227 783167Patch Testing Co-ordinator
Telephone: 01843 235084
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