Chemotherapy, Radiation, and Sun Exposure: What You Need to Know
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Sun Safety During Chemo and Radiation: What You Need to Know

Sun Safety During Chemo and Radiation: What You Need to Know
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Published on July 23, 2025
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Sun safety is always important. Exposure to ultraviolet A (UVA) and ultraviolet B (UVB) rays from the sun damages skin in ways that can lead to wrinkles, sunburns, and skin cancer.

 More than 9,500 people are diagnosed with skin cancer every day in the United States.


Protecting your skin from the sun is even more crucial during cancer treatment. "Some cancer therapies make patients very prone to sunburns," says Jonathan Leventhal, MD, the director of onco-dermatology at Smilow Cancer Hospital at Yale School of Medicine in New Haven, Connecticut. Radiation, certain chemotherapy drugs, and other cancer medications like epidermal growth factor receptor (EGFR) inhibitors and BRAF inhibitors make skin highly sensitive to the sun, he says. The sun can also aggravate rashes caused by radiation therapy and targeted therapy.

How Chemo and Radiation Affect Sensitivity to Sun

Both chemotherapy and radiation therapy make the skin more sensitive to UV radiation from the sun. Other types of medicines, including immunotherapy and targeted therapy, can have the same effect. Drug-induced light sensitivity happens when sunlight activates some of the ingredients in cancer drugs.

A phototoxic reaction is the most common risk from chemotherapy and sun exposure. With this type of reaction, UV light exposure changes the chemical makeup of the chemotherapy drug, causing it to release energy that damages the skin.

 Within hours after getting the chemotherapy drug and being outside in the sun, a person may find that areas of sun-exposed skin (such as the face, chest, arms, and legs) have turned red and swollen as they would with a sunburn.

Photoallergic reactions are like allergies to the sun. They're less common than phototoxic reactions. Within one to three days after a person receives the cancer drug and is exposed to the sun, the skin erupts in an eczema-like rash. Repeated exposure to the drug and sun can make the rash spread.

The chemotherapy medications that are most likely to cause sun sensitivity are:

  • Dacarbazine
  • Fluorouracil (5-FU)
  • Methotrexate
  • Nab-paclitaxel
  • Vinblastine
The combination of radiation therapy and sun exposure also causes phototoxic reactions. As little as 10 minutes outdoors after radiation treatment without adequate sun protection can damage the skin.

 Sun exposure after either chemotherapy or radiation therapy can result in painful skin rashes and sometimes blisters, says Dr. Leventhal.

People who are taking certain cancer drugs or who are on radiation therapy are usually advised to avoid direct sun exposure during treatment, and for a period of time afterward.

Sensitivity to Heat

Heat may be a problem, too. Some cancer treatments, including hormonal therapies, make it harder for the body to regulate temperature, causing increased heat sensitivity.

 Cancer drugs may also cause sweating, flushing, and dehydration during warm weather. "Keeping hydrated and minimizing sun exposure are essential," says Leventhal. Stay inside in the air conditioning when it's hot outside, and avoid very warm places like steam rooms, saunas, and hot tubs.

Sun Safety Tips

It's not necessary to avoid being outdoors altogether, but being careful about sun exposure can prevent burns and rashes during cancer treatment.

Limit Time in the Sun

Plan outdoor activities during times when sunlight is weakest, such as early in the morning or late in the afternoon. The hours of 10 a.m. to 4 p.m. are when most UV exposure and sun damage occur.

Try to avoid direct sunlight by staying in the shade, such as under an overhang, tree, or umbrella. Remember that water, sand, and snow also reflect the sun's rays onto the skin and can cause severe burns.

Apply Sunscreen

Before going outside, apply a generous amount of sunscreen with a sun protection factor (SPF) of 30 or higher, broad-spectrum UVA/UVB protection, and water resistance — even on cloudy days.

"Sunscreen should be applied to all exposed skin, with frequent reapplication, especially after swimming and sweating," says Leventhal. Add an SPF 30 or higher lip balm to shield your lips from sun damage.

Cover Up

Wear ultraviolet protection factor (UPF) clothing, including lightweight long pants and long-sleeved shirts that are tightly woven so they don't let in UV rays. Completely cover any areas of skin that have been exposed to radiation. Protect your head and face with a wide-brimmed hat or scarf and UV wraparound sunglasses.

Stay Hydrated

Cancer treatments like chemotherapy and radiation and their side effects, like vomiting and diarrhea, increase the risk of dehydration. Heat and sun exposure deplete the body of fluid even more. Drink cool water or a sports/electrolyte drink often while outside to stay hydrated.

Signs and Symptoms of Excess Sun Exposure

Spending too much time in the sun can lead to sunburn, sun poisoning, heat exhaustion, and heatstroke. Common symptoms of too much sun exposure include:

  • Skin that looks pink or red, or that feels warm or hot to the touch
  • Pale and clammy skin

  • Swelling under the skin
  • Fluid-filled blisters
  • Headache
  • Fever
  • Nausea
  • Tiredness
  • Weakness

  • Dizziness

  • Fast heartbeat or breathing

If you experience any symptoms like these, go inside to cool down and drink fluids. Get medical assistance if symptoms don't improve.

Can Sun Exposure Affect Cancer Treatment?

It's not likely. "The sun itself shouldn't impact the effectiveness of cancer treatment," says Leventhal. But sun exposure can worsen the rashes that cancer treatments like chemotherapy, targeted therapy, and radiation therapy sometimes cause. That's why it's best to avoid sun exposure while you’re undergoing treatment.

What About Vitamin D?

One benefit to being out in the sun is that the skin produces vitamin D when exposed to UV rays. This vitamin maintains bone and muscle strength, and it helps protect the immune system and the nervous system.

 The recommended dietary allowance (RDA) of vitamin D for adults ages 51 to 70 is 600 international units (IU), and for adults over 70 it's 800 IU daily.

While undergoing cancer treatment, the safest way to get vitamin D is from a supplement. You can also incorporate vitamin D–rich foods into your diet, such as fatty fish like salmon, trout, and tuna. Wild-caught fish tend to have higher levels of vitamin D than farm-raised. Fortified cow's milk, almond milk, and soy milk are also good dietary sources of vitamin D.

The Takeaway

  • Sun safety is always important, but it’s especially so during cancer treatment. Chemotherapy, radiation therapy, and some other cancer medications make the skin more sensitive to the effects of UV light.
  • Too much sun exposure can cause skin rashes, blisters, and burns.
  • Try to stay out of the sun between the hours of 10 a.m. and 4 p.m. Wear sun-protective clothing and sunscreen while outdoors, and drink extra water to prevent dehydration.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Ultraviolet Radiation and Skin Cancer. Cleveland Clinic. November 16, 2022.
  2. Skin Cancer Facts and Statistics. Skin Cancer Foundation. February 2024.
  3. Sibaud V. Anticancer Treatments and Photosensitivity. Journal of the European Academy of Dermatology and Venereology. June 23, 2022.
  4. Cancer Treatment and Photosensitivity. Moffitt Cancer Center. May 20, 2022.
  5. Fernandez L. Sun Protection Is Crucial During, After Treatment. University of Rochester Medical Center. August 10, 2017.
  6. Staying Safe in Extreme Heat When You Have Cancer. Fox Chase Cancer Center. July 11, 2024.
  7. Schlembach P. Staying Safe in the Summer Heat: 5 Tips for Cancer Patients. MD Anderson Cancer Center. July 15, 2021.
  8. Ultraviolet (UV) Radiation and Sun Exposure. U.S. Environmental Protection Agency. March 20, 2025.
  9. Sunburn. Mayo Clinic. June 7, 2024.
  10. 5 Spots You’re Probably Forgetting to Put Sunscreen. Cleveland Clinic. June 19, 2023.
  11. Staying Safe in the Summer Sun: 5 Tips for Cancer Patients. Beaufort Memorial. June 15, 2023.
  12. Heat exhaustion and heatstroke. NHS. August 12, 2022.
  13. Sun Safety and Vitamin D. American Cancer Society. June 26, 2024.
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Blair Murphy-Rose, MD

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Blair Murphy-Rose, MD, is a board-certified dermatologist in New York City and the founder of Skincare Junkie. She is an accomplished cosmetic, medical, and surgical dermatologist, specializing in leading-edge facial rejuvenation techniques, including injectable fillers and botulinum toxin injections, advanced laser procedures, noninvasive body contouring, and removing lumps and bumps with precision. She is an expert in the treatment and detection of medical conditions, including skin cancer, acne, rosacea, eczema, and psoriasis. Dr. Rose believes in a comprehensive approach to skin health and incorporating a skin-care routine tailored specifically for each individual and utilizing a wide array of tools to target specific skin concerns.

Rose has been published in peer-reviewed journals, including the Journal of the American Academy of Dermatology, Dermatology Surgery, and Pediatric Dermatology, and has been featured in numerous publications, including Vogue, Elle, Allure, Cosmopolitan, Self, Women’s Health, The Wall Street Journal, and The New York Times.

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Stephanie Watson

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Stephanie Watson is a freelance health writer who has contributed to WebMD, AARP.org, BabyCenter, Forbes Health, Fortune Well, Time, Self, Arthritis Today, Greatist, Healthgrades, and HealthCentral. Previously, she was the executive editor of Harvard Women’s Health Watch and Mount Sinai’s Focus on Healthy Aging. She has also written more than 30 young adult books on subjects ranging from celebrity biographies to brain injuries in football.
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