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I am Dr. SS. I will try my best to help you.
When did you first notice it?
How large is it?
Does he have any other symptom?
There are a few probables.
This can cause redness.
If it does not improve & continues to increase, I would suggest to get it checked by doctor.
In babies infantile eczema can occur.
It often improves when the babies grows up.
Please feel free to ask if you have any follow up question.