Oatmeal soothes, nourishes, and moisturizes dog's skin (human skin too so feel free to use this in your own tub), one of our dogs suffers from allergies and a nice oatmeal and Epsom salt bath takes away the itching and keeps her comfortable. I give them an oatmeal bath about every 3 weeks. If you have an itchy dog, talk to your vet about causes and treatments, and ask if an oatmeal bath will help them too.
Step 1: Grind oatmeal to powder
I usually fill my Vitamix halfway with oats and use the tamper to get all the oats ground. If your machine doesn't have a tamper, stop the machine and use a spatula a few times around the edges. Do a few batches and you'll have plenty to last awhile.
Transfer to an airtight container and store at room temperature.