You have asked good questions and you are certainly not freaking out for no reason.You baby son appears to have a form of eczema known as seborrhoeic eczema which is not an allergic kind. So changing his formula will make no difference. Usually this eczema diasappears by the age of 6 months. If the rash is troubling your baby you can use a very mild cortisone cream called Mylocort. Apply the cream once or twice aday until the rash is clear then only when needed after that.
The sacral dimple you mention may be of no concern but it also may indicate the possibility of a defect in the lower part of a baby's spine,a condition called spina bifida or there may be a troublesome sinus that develops called a pilonidal sinus. So for these reasons it would be best to ask your paediatrician to just check your baby just to be on the safe side.
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