This rash does not sound like it is due to a milk allergy from your description.It is difficult to be sure about the cause of this rash without being able to see your son, but it may be due to a viral rash called molluscum contagiosum.Another possibility is that the rash is due to flea bites. Have a look at pictures of 'molluscum' on Google and see if you think your son may have this rash. If you are concerned take your son to see your paediatrician.
The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal
advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.