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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Is Sunshine Bad for Dogs with Cancer?

Updated: August 9th, 2019

There’s a common myth that sunlight is bad for dogs with cancer. But, that’s not true. According to Dr. Dressler in the Dog Cancer Survival Guide (Chapter 13), the only dogs who shouldn’t be exposed to the sun are those with Squamous Cell Carcinoma or Hemangiosarcoma. For all other cancers, dogs should be free to relax in the beautiful sunshine- with some precautions, of course.

Why is Sun Good for Dogs with Cancer?

Sunlight is good for your dog’s body. A few rays of sunshine each day helps the body create Vitamin D.

Yes, Vitamin D can come from multivitamins- or milk- but they’re no comparison to a little sunshine each day.

The hormonal form of Vitamin D attaches to the outside of cancer cells- and could slow angiogenesis (when cancer tumors make new blood vessels so they can take the nutrients from our dog’s bloodstream), cancer cell division, and metastasis (the spread of cancer to other parts of the body).

How Much Sun is Good for Dogs with Cancer?

When we look at the recommendations for us… humans with light skin should spend 10-30 minutes in the sun each day for a good amount of Vitamin D. Humans with dark skin might require several hours to get the same amount.

We can apply the same rules to dogs. Dogs with light coats (light skin), should stay out in the sun for 10-30 minutes… and dogs with dark coats and dark skin can stay out in the sun for several hours.

Natural sunlight is best. But, you’ll need to take some precautions.

We don’t want our dogs to become overheated. If you’re planning on your dog being outside for longer than 30 minutes in 75 degrees Fahrenheit (or warmer), their hair should be trimmed short to prevent heatstroke.

Dogs with short snouts, like Pugs and French Bulldogs, are more prone to overheating than dogs with long snouts. You should be especially careful with them. And, no dog should be permitted outside for longer than a few minutes if the temperature is higher than 85 degrees Fahrenheit.

If natural sunlight isn’t an option for your dog, you can grab a UVB light therapy lamp. The UVB therapy lights have been used to treat depression in dogs when they’re not able to get ‘the real thing.’ And, scientists have found they could help with all different forms of cancer.

Can I Give My Dog Vitamin D Supplements?

Dr. Dressler doesn’t recommend supplementing with Vitamin D. When your dog takes a Vitamin D supplement, there isn’t much that reaches their bloodstream.

And, the amounts that do reach the bloodstream could be toxic.

The Bottom Line on Sunlight

Instead, unless your dog has Squamous Cell Carcinoma or Hemangiosarcoma, you should set some time aside for your dog to enjoy the sun. Let the wind blow through their fur. Help them enjoy the beauty of the outdoors. And, keep their spirits high.

If you’re looking for more information about Vitamin D and sunlight, you can read a few of the studies Dr. Dressler and Dr. Ettinger used for The Dog Cancer Survival Guide here.

Leave a Comment

  1. Randy Ringold on March 8, 2018 at 8:22 am

    Barb is correct that dogs/cats ability to synthesize VitD from UV radiation is extremely limited and the primary source is diet. Howe published his findings on this topic in 1994 ( The protein source provides most of the dietary VitD and since food is so heavily processed, dogs are frequently found to be insufficient. Tufts published their findings that most brands of dog food do not provide enough VitD ( Vitamin D sufficiency is vital to prevent many inflammatory diseases, cancer being just one. There is a wonderful new publication showing Vitamin D sufficiency helping with atopic dermatitis ( I encourage your readers to learn more about Vitamin D for their pets and for themselves.

  2. Barb on March 6, 2018 at 5:08 am

    It seems there is a difference of opinion/difference in results from science as to a dog’s ability to absorb vitamin D from the sun. Many leading veterinarians state that dogs can not absorb vitamin D from the sun, therefore they need to rely on the foods they eat and the supplements they take to get adequate amounts of vitamin D in their diets. Yet this article here maintains that dogs CAN get vitamin D from the sun. Which is correct or don’t we really know yet?

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