It is always difficult to diagnose a skin condition without being able to see your child. You do not mention whether the rash is itchy. From your description this at first sounded like an allergic rash called 'urticaria'.[Look this up on Google] but then you mention that you also have the same rash. So the possibility is that this may be a ringworm. It would be best to ask your doctor to have a look at your son's rash and to make a diagnosis so that the correct treatment can be given.
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