why do babies get acne? what causes it? and when will it go away??
my son is also 3 weeks

they get acne because of the changes in their hormone levels after birth. it is the same principle as why teenagers get acne – just a change (increase/decrease) in hormonal levels. it will usually go away in a few weeks and is usually nothing to worry about at all. my daughter got acne at about 3 weeks old and had it until she was about 2 months old.