Marshmallows are OK for dogs in moderation as long as they don't contain xylitol.
Although it's recommended to feed dogs marshmallows but feeding a dog marshmallows on occasion as a treat is okay.
My dog eats marshmallows as an occasional treat and has done so for years.
Just be sure to avoid marshmallows that have xylitol, if possible as xylitol is an artificial sweetener that is highly toxic to dogs, even in small amounts and can cause seizures, liver failure and death.
Marshmallows are also high in sugar and can lead to dental problems, obesity and digestive issues in dogs, especially if consumed in large amounts.
The marshmallows that contain xylitol are the sugar free and diet varieties of marshmallows.
Standard or regular marshmallows don't contain the xylitol so they are safer for dogs to eat.
Some dogs might have trouble digesting marshmallows and may get stomach upset, vomiting or diarrhea.
But as long as the marshmallows don't contain xylitol the dog will be fine.
Although a large quantity of marshmallows when consumed by dogs can cause a digestive blockage.