Diy Dog Itch Relief Shampoo . Directly apply the paste to your dog’s affected areas and gently rub it in. Instructions place baking soda and corn start in a large bowl, mix well with a spoon. Homemade Dog Shampoo For Itchy Skin Diy dog from www.pinterest.com Place 5 drops of lavender or a dog safe essential oil in the mixture. Pour boiling water over dried lavender flowers in a vessel. 1/2 cup organic apple cider vinegar.