Sun Exposure During Radiation Therapy: What to Know

Radiation is aimed at one part of the body, and the skin over it takes a share of the dose.

NCI describes what that looks like. The skin in the treatment area can become dry and peel, itch, and turn red or darker. It may look sunburned. It may swell. Sometimes it becomes painful and wet, which NCI calls a moist reaction, and that skin can get infected.

Now add real sunlight on top of that. You are asking skin that is already inflamed to handle a second injury in the same place.

MedlinePlus gives a short, concrete list for skin in a radiation field. The sun items are:

• Keep the treatment area out of direct sunlight while you are having treatment.
• Wear clothing that protects you from the sun — a hat with a broad brim, a long-sleeved shirt, long pants.
• Use sunscreen.

Clothing does most of the work here. A loose cotton shirt over a treated chest or shoulder is more reliable than remembering to reapply anything, and MedlinePlus separately advises loose, soft fabrics next to the skin rather than tight or rough ones.

The rest of your body needs ordinary sun sense, not special measures.

Here is where people get caught out, because two pieces of advice sit next to each other and seem to disagree.

MedlinePlus says do not use lotions, ointments, makeup, or perfumed powders and products on the treated skin, because they can irritate it or interfere with treatment. It then says to ask your provider what products you can use, and when.

NCI's skin guidance lands in the same place. Use only recommended skin products, and if you are having radiation, ask which ones to avoid before a session.

So sunscreen is not banned. It is on the list of things your radiation team decides about, along with which brand and at what point in the day. Ask once, at the start, and you will not have to guess for six weeks.

While you are asking, MedlinePlus adds a few more for the treated area: wash gently with mild soap and lukewarm water, pat dry rather than rub, use an electric razor if you shave there, and skip adhesive tape, bandages, heating pads, and cold packs.

Radiation is not the only reason to be careful in the sun during treatment.

NCI notes that some types of chemotherapy can make you sunburn easily, and gives that a name: photosensitivity. That affects all of your skin, not one rectangle of it.

If you are on a drug that does this, the protection has to be general — sunscreen on exposed skin, sun-protective lip balm, long sleeves, a wide-brimmed hat, and shade in the middle of the day. NCI names all of these.

Tanning beds are not a middle ground. They are a stronger version of the same problem.

One more thing worth recognizing, because it can appear long after you have stopped thinking about radiation.

NCI describes radiation recall: if you had radiation therapy in the past, the area of skin that was treated may become red, blister, peel, or hurt. It can turn up in an old field with no new injury.

If that happens, it is a reason to call your team rather than to treat it at home.

MedlinePlus is direct on the long view. The treated area will be more sensitive to the sun, and you will be more at risk of skin cancer in that area.

What it does not do — and what NCI does not do either — is put an end date on that. There is no published number of months or years after which the area goes back to normal.

That absence is worth naming rather than filling in with a guess. Ask your radiation oncologist how long they want you protecting that patch, and whether they want it checked at follow-up appointments.

Tell your team about any skin changes, and about any break or opening in the skin. NCI adds that radiation-treated skin that becomes painful and wet needs attention, because it can become infected, and your nurse may prescribe dressings or antibiotics.

• Which sunscreen can I use on the treated area, and starting when?
• Should I avoid putting anything on the skin before a session?
• Do any of my other cancer drugs make me burn more easily?
• How long after treatment should I keep this area covered?

This is general information. Your care team's specific instructions for your treatment always take priority.

• MedlinePlus — Radiation therapy: skin care
• NCI — Skin and Nail Changes during Cancer Treatment
• NCI — Radiation Therapy Side Effects