Dermatology - Photoinvestigation for photosensitivity

This leaflet has been written to help you understand your photoinvestigation test. We hope it will help you to understand why, how and where the tests will be carried out.

Why do I need these tests?

Skin is sometimes sensitive to light. The light might cause discomfort, sunburn or rashes. The tests will show how sensitive your skin is to light.

We can use these results to:

• Help diagnose your specific condition
• Show the severity and type of sensitivity that you have
• Discuss the treatment options available to you

How should I prepare for the tests?

• For at least five days before you come for photoinvestigation tests, if possible, please do not take any anti-inflammatory or antihistamine tablets or apply steroid creams to your back or arms. These tablets and creams can interfere with the tests. Please telephone the unit in advance if you have any concerns about this
• Please bring along any sunscreen creams or other products that contain sunscreens e.g. facial cosmetics that you use, together with a list of any medication that you are taking. We need to test the sunscreens on your skin on the first day of your test. This is important
• Please bring along an old T-shirt that you can change into after the tests. This is because the ink markings we use can sometimes rub off onto clothing leaving black marks 
• Please bring along any photographs you have taken of your rash
• Please do not have a bath, shower or go swimming during the four days that we are testing your skin
• There can be quite a lot of waiting. You may like to bring a cold drink, something to eat and something to read/do
• We will be sticking tapes and writing on your back. If necessary we may have to shave your back
• The staff doing the testing are men and women. If you prefer all the testing to be done by women, please let us know as soon as possible and we will try to arrange this
• If you have any access needs (e.g. interpreter needs, impairment needs etc) please telephone the unit and let us know

Checklist

Please telephone to confirm the appointment and bring the following with you:

• Your appointment letter
• A list of your medication
• Your sunscreens and any products that you use containing sunscreens e.g. moisturisers with an SPF number
• Any photographs of your rash
• An old T-shirt
• A cold drink and something to read/do
• Children should bring a pair of shorts
• Coins for vending machines and parking meters

How long will it take?

You will be attending the unit daily for four days while we do all the tests. There will be some waiting in between tests, so it is a good idea to bring along something to read and a drink. There is a café in the hospital and we will try to let you know if there is time to pop out.

How will the tests be carried out?

Taking the history of your condition

The doctors will take a detailed history of your condition, if this has not already been done. This will take about 45 minutes. The doctor will ask lots of questions about your rash for example:

• Which month of the year does you rash start?
• How long do you have to be outside before you get your rash?
• How soon after being outside do you start to see your rash/feel symptoms?
• How long does it take for your rash to fade?

The doctor asks these questions because there are lots of sun allergies that are very similar and your answers will help the doctor diagnose your condition.

When the doctor has finished, we will start the photoinvestigation testing using a number of lamps. These lamps shine different sorts of light onto your skin.

Light threshold test

Monochromated light testing is to see how sensitive you are to a range of types of light of different wavelengths.

• We will do this test on Monday or Wednesday
• It takes between 1.5 to 3 hours
• We will shine many small patches of light onto your back
• The test may cause small (less than 1cm) spots of reddening on your back
• This redness will rapidly fade over a few days, although small tanned spots may take longer to disappear.
  
  

Provocation test

For provocation testing we use two ultraviolet lamps to see whether we can bring out a patch of your rash to help diagnose your condition.

• We will shine a different type of light on each forearm
• This will normally be done on Monday, Tuesday and Wednesday
• It will take about 25 minutes to do both arms

Patch and photopatch allergy test

Patch and photopatch testing looks at whether you are allergic to sunscreens or non-steroidal anti-inflammatory gels and creams.

• Small patches will be put on your back on Monday
• On Tuesday we will remove the patches
• We will then shine a small amount of ultraviolet onto half the area
• We will look at how your skin reacts on Wednesday and Thursday
• The test may cause small patches of reddening on your back

Blood and urine tests

The fourth test is a blood and urine test. There are some rare immune and biochemical conditions that can make people sensitive to light. We can detect these conditions from blood and urine samples. We will need to collect a urine sample from you and take some blood samples.

Childrens blood samples

Taking blood samples from young children can be stressful for the child. We will ask any young children to go to a specialist children’s clinic located approximately 5 miles from the main hospital. You will need to make your own way to this clinic and we will provide you with details of where to go.

Training doctors in photobiology

The photobiology unit is a training unit. We train dermatologists in this very specialised area. These comprise our own qualified doctors who will be involved in your care during the week. Sometimes there are also visiting doctors. If you are not happy for them to be present, please let the staff know.

Clinical Trials

We sometimes have clinical trials (research) taking place on the unit. This research may be relevant to you, e.g. questionnaire surveys to assess the impact of photosensitivity on patients’ lives and potential new treatments for photosensitivity. We will ask you whether or not you would like us to contact you if any new research takes place that is relevant to your condition. If you are happy for us to contact you, then we will keep your contact details on our database and will write to you if there is something of potential interest to you.

Where is the photoinvestigation carried out?

You should come to the photobiology unit which is on Level 0 (ground floor) of the Barnes Building. Go to the Pink Area and follow signs for the Photobiology Unit.

Please bring your appointment letter with you and report to the Photobiology Unit reception.

Contact Information

Photobiology Unit Booking Office - 0161 206 4081 between 9am - 3pm (answer machine at other times)
Photobiology.salford@nca.nhs.uk

IMPORTANT

Please let us know if you are not going to be able to come for the tests. We have long waiting lists and can only test a few patients each week. If you do not attend the appointment without warning the unit, we will not send you another appointment.