Excessive Sun Exposure Causes Sunburn and Skin Cancer in Dogs

Like humans, dogs exposed to the sun can develop actinic keratosis.

Choose a fragrance-free sunscreen that protects from UVA and UVB rays, preferably one formulated for dogs. Nikolai Tsvetkov/Shutterstock

Q: I recently adopted Rosie, a greyhound who is mostly white. Earlier this summer, she was out in the sun too long and got sunburned. When we go on vacation together later this summer, I'll try to keep her inside as much as possible between 10 a.m. and 4 p.m., but I’m worried about her getting sunburned.

Is dog sunscreen available? Can dogs get skin cancer from too much sun?

A: The answer to both questions is yes.

You can shield Rosie by dressing her in ultraviolet-protective pet clothing and applying sunscreen. Choose a fragrance-free sunscreen that protects from UVA and UVB rays, preferably one formulated for dogs.

It’s important to avoid excessive sun exposure because of the problems it causes, from a painful sunburn to skin cancer.

Like humans, dogs exposed to the sun can develop actinic keratosis, a firm, thickened, crusty skin lesion that may progress to skin cancer.

The most common sun-related skin cancer in pets is squamous cell carcinoma.

Chronic exposure to sunlight can also cause hemangioma or hemangiosarcoma of the skin. “Hem-” refers to blood, “-angio-” to vessels, and “-oma” to a mass. So a hemangioma is a benign tumor of blood vessels, while a hemangiosarcoma is the malignant version.

A hemangioma appears as a small, flat, red or purple discoloration of the skin. It may grow into a large nodule that ulcerates and bleeds, and it may progress to a malignant hemangiosarcoma. Usually, you'll see multiple tumors.

Rosie is at increased risk of sunburn and UV-induced skin cancer because her hair is short and her pale skin contains little protective pigment. You are wise to safeguard her from the harmful effects of the sun.

Q: I order supplements for my pets from online pharmacies that ship them through the mail to my home. It’s been unusually hot this summer, which makes me wonder whether heat can affect the quality of supplements sent through the mail. Should I be concerned?

A: Some supplements are affected by heat and humidity, so you are right to be concerned.

Supplements that contain probiotics, the good bacteria that work in the intestines, deteriorate when subjected to excessive heat or humidity.

Water-soluble vitamins, including the B vitamins and vitamin C, are also very sensitive to heat and humidity. High humidity can cause vitamin C to lose its potency within a week.

The omega-3 fatty acids in fish oil become rancid when exposed to heat.

SAMe and creatine can be broken down by moisture, particularly if the packaging doesn’t protect them well.

Minerals and glucosamine-chondroitin products are fairly stable in the heat.

If you receive a supplement that is discolored or a bottle of pills or powder that contains drops of liquid, the supplement was probably damaged by heat or humidity. Also, degraded B vitamins emit a sulfur odor, and damaged vitamin D has a fishy scent.

I suggest you buy your pets’ supplements from your veterinarian, at least during the summer. Don’t leave them in your car while you run errands, because the car’s interior heats up quickly. Likewise, don’t leave dry pet food in a hot car because the heat can make the oils in the kibble rancid.

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