Your dog may be eating snow because he likes the taste and the cold feeling, Calvin. Or maybe it’s just fun for him. Eating snow is generally harmless for most dogs and is usually not the cause of raw, swollen gums—unless your dog is also eating pieces of ice that are cutting or scraping his gums. Keep supplying him with plenty of fresh, clean water to drink. If you’re concerned that this habit may be harmful, you may also consider watching him closely when he’s outside and distracting him from eating the snow.
We would also suggest you have your dog’s teeth and gums examined. Your veterinarian may be able to determine whether there are other factors contributing to your pet's tooth and gum problems and help you to find a solution.