Kia Benson, DVM
Associate Veterinarian, Clinical Toxicology
As our own Candi Amundson, CVT and Senior Veterinary Information Specialist mentioned in her June blog, sunburn can be a big problem for animals as well as humans. Let’s take an in-depth look at this medical issue that often flies under our radars until a problem develops.
Sunburn
Sunburn, or Solar Dermatitis as it is known in medical terms, is an inflammatory skin disease caused by prolonged exposure to ultraviolet (UV) radiation. UV radiation penetrates deeply in cells and causes changes within the cells that lead to sunburn, skin aging, and skin cancer.
The solar spectrum is comprised of approximately 40% visible light rays, 50% infrared light rays, and approximately 9% ultraviolet light rays. UVA radiation causes skin aging and is also likely to cause skin cancer. UVB causes redness and sunburn and is a major risk factor for all types of skin cancer. Duration of exposure to the sun plus the intensity of the sun at the time of exposure also influences the degree of skin damage that can result.
Sun damage to cells causes inflammation, which perpetuates and even amplifies the initial injury to the tissues. Prolonged and repeated exposure to UV radiation with its subsequent cellular damage can alter the skin’s immunological system, resulting in skin cancer.
Melanin in pigmented skin absorbs UV rays, which can help prevent deeper UV light penetration and cellular damage. As a result, animals with a non-pigmented skin/white haircoat are more at risk than those with darker haircoats. Animals with thinly-haired or very sparse haircoats like Chinese Crested dogs or Sphynx cats are also in danger. Lastly, animals whose long hair gets shaved for cooling in summer or those shaved for surgery, and animals with hair loss from allergies can be in jeopardy from too much sun.
Both companion animals and farm animals can be hurt by too much sun exposure. In today’s blog we’re going to focus on cats and dogs. In part 2, we’ll focus on horses and pot-bellied pigs.
Cats
Cats don’t have to go outside to risk a sunburn. Any cat who has areas of white haircoat or a thinly-haired/sparse haircoat is at risk of sunburn, even if the cat just sunbathes indoors. While glass does offer some sun protection, it is not sun proof. Damage over long time can still occur.
Solar dermatitis in cats most commonly affects the ear tips, bridge of the nose, skin surrounding the lips, and the eyelids. Lesions that develop are initially red and not itchy, but can progress to crusty, peeling, itchy lesions that look ulcerated or eroded. The lesions become tender to the touch, and secondary infection can develop. If the ears are affected, the outer portions can begin to curl back.
In their initial mild stage, sunburn-related lesions can be treated with steroids (systemic or topical) to ease discomfort and antibiotics (systemic or topical) to treat any secondary infection.
Prolonged sun exposure can turn these lesions into a type of cancer called Squamous Cell Carcinoma (SCC). Skin biopsies will be needed to diagnosis that the lesions have become cancerous.
Small, non-cancerous lesions may be treated via surgical removal, laser or cryotherapy (freezing). Pre-cancerous or cancerous lesions require aggressive treatment as Squamous Cell Carcinoma is a very invasive, fast-growing cancer that is often resistant to healing. Aggressive surgical removal (e.g. require amputation of the outer portions of the ears or parts of the nose), and/or laser therapy are usually needed.
Postoperatively, aggressive sun protection in the future is required to prevent the development of new lesions. Unfortunately, a cat with previous solar dermatitis is at risk of additional lesions developing months or even years after the initial exposure.
Dogs
Like cats, any dog who has areas of white haircoat or a thinly-haired/sparse haircoat is at risk of sunburn. Short-coated breeds (e.g. pit bulls, boxers, dalmatians, bulldogs, etc.) that have areas of non-pigmented skin are also more vulnerable than longer-coated breeds.
In addition to ears, bridge of the nose, and eyelids, sun damage in dogs can occur around the lips. Thin hair anywhere on the dog – the flanks, in the armpits, on the abdomen and groin and inside legs – will be more prone to damage. Dogs who routinely lay on concrete or light surfaces can suffer sunburn from reflected solar rays. Some dogs that prefer to lie on only one side of their body may have more severe lesions on that sun-exposed side, and dogs that mainly like to lay on their backs will be prone to worse lesions on their belly. You might see a sharp demarcation between areas of normal skin with protective (dark) pigment and damaged nonpigmented skin.
Lesions initially present as red areas that are not itchy. With chronic exposure to the sun, blackheads, ulcers, crusts and scarring or thickened skin can develop. Secondary infection is common. Over time, the lesions can progress to sun-induced cancers like Squamous Cell Carcinoma (SCC), Hemangioma, or Cutaneous (skin) Hemangiosarcoma.
In their initial mild stage, sunburn-related lesions can be treated with steroids (systemic or topical) to ease discomfort and antibiotics (systemic or topical) to treat any secondary infection.
Treatments for chronic solar dermatitis in dogs include oral medications like non-steroidal anti-inflammatory medications (NSAIDs), retinoids/vitamin A, and Beta carotene. These medications may have side-effects. A topical anti-cancer immune modifier called Imiquimod (Aldara®) might also be of benefit. Surgical removal, cryotherapy, or laser removal may also be used. Any lesions that have been diagnosed as cancerous require aggressive surgical removal and/or laser therapy.
As with cats, a dog with previous solar dermatitis is at risk of additional lesions developing months or even years after the initial exposure.
Prevention
The keys to preventing sunburn/skin cancer include restricting an animal’s exposure to the sun, especially during the time of the most intense UV radiation – typically between 9 AM to 3 PM. Other measures like drawing the shades or blinds during that part of the day, applying UV protective film to the windows that get the most sun, providing shelter in the form of buildings or trees to allow animals to get out of the sun, and avoiding sources of reflected sunlight (e.g. white concrete flooring in a dog run, sunlight reflecting off water) can also help.
While it may be helpful for a dog to wear a T-shirt when outside, it is often impossible to cover all at-risk areas of the skin. Clothing designed for companion animals to help keep them cool and avoid the sun has been a trending item over the last few years and may be an option for at-risk animals.
Appropriate sunscreens can be used on dogs and cats, though they may be less effective in cats because of their grooming habits. Checking the ingredients in a sunscreen product is critical. Human sunscreens often contain aspirin-like compounds (e.g. octyl salicylate), which can be toxic if ingested by dogs or cats. Cats are especially sensitive to aspirin and aspirin-like compounds. Even sunscreens for babies may be hazardous to animals.
Look for sunscreen products have been specifically created for pets that protect against both UVA and UVB radiation with an SPF of at least 30. Make certain that the product labeling specifically states that it is appropriate and safe for cats and dogs. Avoid any sunscreen that has ingestion warnings. When using a pet-appropriate sunscreen, apply it 10-15 minutes prior to exposure and re-apply it frequently during solar exposure.
If you are not certain whether or not a sunscreen is safe to use on your pet, please consult a veterinarian or Pet Poison Helpline® before trying it out.
The information in this blog is not a substitute for a physical examination and consultation with a veterinarian. If you are concerned about possible signs of sunburn/solar dermatitis in your pet, please consult your veterinarian. Consultation with a veterinary oncologist is recommended if your pet has been diagnosed with any form of skin cancer.
