My 3 and a half month old baby had milia at birth. The bumps have disappeared, but they seem to be coming back today, is that normal?

Yes, it is possible for milium to disappear and then reappear. If the bumps persist for more than 3 months, it would be best to consult a doctor. The causes of milium are not fully understood, but hormones may play a role in some cases. It is important not to apply oily or moisturizing creams on milium, but instead wash the affected areas with warm water a few times a day and gently pat dry with a soft towel. Avoid using cleansers, picking or scratching the bumps. If you have any further questions or concerns, feel free to reach out for more information.