Try this: Nettles

A particularly rich source of minerals and vitamins (especially iron), nettles are good as a blood purifier and are helpful with skin conditions and allergies. You can also forage and pick your own young nettles— wearing gloves of course (uncooked they sting)! Cover with water and simmer for 10 minutes. When cool, add a few tablespoons of the liquid and cooked leaves to your dog’s food as an overall tonic.