M.H.
My son has the same issue, Seborrheic Dermatitis. I took him to five dermatologists (because his hair was falling out in clumps...bald spots all over his head). We started doing the tar shampoo and all sorts of conventional things. I failed to take a look at alternatives because I panicked. I'm a holistic health nutritionist, so I chilled out I gathered the information I needed to get a handle on this properly. Seborrheic Dermatitis shows up because of an overgrowth of yeast. When it shows up in a child that is so young, it can be traced back to either parent having had yeast problems. It all comes down to diet. Take out diary and gluten. It's a process, but an important one. See this as a gift, because this can lead to huge issues in the future.
If you have any questions about this just let me know.
Good luck!
M.