Sunlight can sometimes trigger or worsen graft versus host disease in the skin after a donor stem cell transplant. We explain why patients are advised to take extra care – and how you can still enjoy being outdoors safely.
Sunlight and GvHD
With hot, sunny spells becoming an increasingly familiar feature of the British summer, many of us will be spending more time outdoors – meeting friends in the park, sitting in the garden or simply enjoying the sun.
But if you have had a donor stem cell transplant, you may have been advised to take extra care in the sun. Spending a lot of time in direct sunlight can sometimes trigger graft versus host disease (GvHD) in the skin, or cause existing skin GvHD to flare up.
That does not mean you need to spend the summer indoors. Understanding why sunlight matters can help you protect your skin and enjoy the warmer weather safely.
What is GvHD?
GvHD can happen after an allogeneic stem cell transplant, where the cells used for your transplant come from a donor.
The word graft refers to your donor’s cells, while the host is you. After your transplant, the donated cells begin forming your new blood and immune system.
Even when you and your donor are very closely matched, small differences remain between your new immune system and the other cells in your body. Sometimes, the donor-derived immune system recognises some of your healthy cells as different and attacks them. This is what we call GvHD.
GvHD is a common side effect of a donor stem cell transplant. For many people it is mild and can be controlled with medication, although more serious or long-lasting cases can affect quality of life.
Why can sunlight affect skin GvHD?
The skin is one of the parts of the body most commonly affected by GvHD.
Our Patient Services team is often asked why patients are advised to avoid spending too much time in the sun. The simple answer is that the ultraviolet light (UV) in sunlight can sometimes trigger skin GvHD or make existing symptoms worse.
Note: stem cell transplant patients are also advised to avoid too much sun exposure due to an increased risk of developing skin cancers. Always check with your medical team for advice relating to your own personal treatment.
UV can damage proteins, fats and DNA in cells in the outer layer of the skin. The damaged cells then release chemical signals that trigger inflammation. Blood flow to the area increases and immune cells move into the skin, helping to produce the redness, swelling and soreness we associate with sunburn.
After a donor stem cell transplant, those immune cells are part of the new immune system formed from your donor’s cells. The inflammation caused by UV damage may make the skin more vulnerable to attack from these cells, potentially triggering skin GvHD or causing existing symptoms to flare.
Medical professionals do not yet fully understand why some people develop GvHD while others do not. Even people with very closely matched donors can experience it.
This unpredictability can be frustrating, but taking sensible precautions in the sun can help protect skin that may already be more vulnerable after treatment.
What does skin GvHD look like?
Skin GvHD can affect people in different ways, but common symptoms include skin that is dry, red or itchy across several areas of the body.
It can also affect your ability to regulate your temperature. If the skin becomes broken, this may increase the risk of infection.
Having one of these symptoms does not automatically mean that you have GvHD. Skin changes can have many different causes during recovery from a transplant.
However, you should tell your transplant team about any new symptoms or changes to your skin as soon as possible. GvHD can sometimes worsen quickly if it is not treated, and your team can investigate what is causing the change and recommend the right treatment.
Do I need to stay indoors?
Fortunately, protecting yourself from the sun does not mean spending the entire summer indoors with the curtains drawn.
The aim is to avoid unnecessary exposure and protect skin that may be more sensitive following your transplant. The precautions you need will depend on your treatment, medication, stage of recovery and whether you have experienced GvHD before.
You should always follow the individual advice given by your transplant team.
When spending time outdoors, this may include wearing high-factor sunscreen, covering exposed skin and wearing a hat. It may also mean limiting long periods in direct sunlight, particularly if you already have skin GvHD or have been advised that your treatment makes your skin especially sensitive.
Due to an increased risk of skin cancer for stem cell transplant patients, it’s also advised to regularly check your skin for changes such as new or changing moles or growths, rough or scaly patches, or sores that don’t heal.
Is it the heat or sunlight?
Although this advice feels especially relevant during a heatwave, sunlight and heat are not quite the same thing. UV damage comes from the ultraviolet part of sunlight, not heat.
This means sunlight can still affect your skin when the temperature feels comfortable, so it is worth taking precautions even when the weather does not feel exceptionally hot.
Heat can bring its own challenges too. Our GvHD guide explains that skin GvHD can affect temperature regulation, while gut GvHD may cause sickness or diarrhoea, which can increase the risk of dehydration.
If hot weather is making your symptoms harder to manage, speak to your transplant team.
What should I do if I notice a change?
Tell your transplant team promptly if you notice:
- a new rash
- worsening redness or itching
- skin that becomes painful or broken
- a flare of previously diagnosed skin GvHD
- any other change that is worrying you
Do not wait until your next scheduled appointment if your symptoms are new or getting worse.
Our guide also advises reporting any fever immediately, as this could be a sign of infection. Your team may be able to advise you over the phone and, in many cases, save you an unnecessary trip to the clinic.
Enjoying the weather safely
Being told to take extra care in the sun can feel restrictive, particularly when a heatwave lasts for weeks.
But the advice is there to protect your skin and reduce the chance of GvHD becoming more active. Protecting your skin does not mean missing out on a walk, a picnic in the park or time with friends and family. It means planning ahead and following the advice given by your transplant team.
If you are worried about GvHD or any other part of your recovery, your transplant team should remain your first point of contact. Our Patient Services team is also available on our Helpline on 0303 303 0303 or email patientinfo@anthonynolan.org (Monday to Friday, 9am to 5pm).
Written by Jack Hooper. Information reviewed by our medical officers.