Blemishes on your new baby's face aren't necessarily acne, however. Tiny white bumps that are there at birth and disappear within a few weeks are called milia, and they're not related to acne. If the irritation looks more rashy or scaly than pimply, or it appears elsewhere on your baby's body, he may have another condition, such as cradle cap or eczema.
Pimples are raised red spots with a white center that develop when blocked hair follicles become inflamed or infected with bacteria. Blockages and inflammation that develop deep inside hair follicles produce cystlike lumps beneath the surface of your skin. Other pores in your skin, which are the openings of the sweat glands, aren't usually involved in acne.