Sunburn & Sunscreen
Fresh air and sunlight are great for us and our dogs but like many things it needs to be in moderation. Dogs are unable to synthesize vitamin D in their skin with sunlight so they are dependent on dietary sources to meet their vitamin D requirement so they do not need to be in the sun for a specified number of minutes each day.
Avoiding sunburns and choosing an appropriate sunscreen for dogs is especially important for dogs with:
Thin or bare spots
Pink or light-colored noses
Sun worshipers lying on their backs
Dogs can get sunburn and skin cancer so sun exposure needs to be moderated. But more important than sunburn is the risk of over-heating and heat stroke for every dog. Dogs are very inefficient in regulating their body temperature in hot weather. Humans have sweat gland all over their bodies to assist in cooling down, but dogs only have these glands on their nose and pads of their feet and panting being the primary way they regulate their body temperature is very inefficient. Over-heating & Heat Stroke
There are differing opinions on what ingredients should be in the sunscreen used on dogs. There are two things that I have found that is agreed upon; the first is to select a sunscreen specifically made for dogs, and second is to choose a sunscreen that does not have para-aminobenzoic acid (PABA) which is toxic to dogs if ingested.
This is the list of ingredients that I found to be on the “Avoid” list from differing sources. [1,2,3,4]
Para-aminobenzoic acid (PABA),
Exercising Your Dog- What you need to know!
Considerations When Choosing A Sunscreen
While everyone agrees on avoiding PABA there are differing opinions on the ingredients on the “avoid” list above. There are several dog sunscreens that include many of the ingredients on the list above. There are sunscreens that include salicylates but some point out that even a small dose can put your cat into the ICU. 
Dr. Karen Becker recommends “products that contain only zinc oxide for active UVA and UVB ray protection. Unlike some chemical sunscreens that may absorb ultraviolet light, zinc oxide helps reflect and scatter away both UVA and UVB rays from your pet's body. Zinc oxide is found naturally in the earth's crust and is a safe ingredient to help prevent excessive sun exposure.”  But others point out that zinc oxide is toxic to dogs if ingested so they advise against its use for dogs and even humans if you have a dog that likes to like you.
Still another opinion is to avoid all of the ingredients above and instead opt for products using a base of active ingredients which includes carrot seed oil and red raspberry seed oils (not essential oils) which naturally has a high sunscreen protection factor (SPF).
After reading all the differing opinions and having both both dogs and cats I think it best to stay with the safest alternative since I was able to find several truly natural alternatives on the market. And for those DIY inclined there is even a recipe on how to make your own natural and safe sunscreen.
If your dog does get sunburn, “You can treat sunburns with 100% pure Aloe Vera gel.”