Infantile seborrheic dermatitis is another name for the common infant skin condition known as "cradle cap."  It causes scaly skin that is yellow and greasy to form on the baby's skin.
The condition seborrheic dermatitis is what causes dandruff in children, teens, and adults. The infantile condition is most common in newborns to children under the age of 3.  There is no known cause, but there are several things that may be linked with it, which include the yeast known as malassezia, oily skin, immune system problems, extreme weather, and the like.
Seborrheic dermatitis can affect anyone, but the infantile condition usually goes away on its own. The more severe cases should be treated by a doctor, especially if they create red patches, ooze fluids, contribute to hair loss, show signs of infection, or seem linked to the child's inability to gain weight, or present other similar issues. It should also be noted that this condition is not connected with hygiene and it is not contagious.
The duration of the condition varies, but for many children, it usually only lasts the first 6 weeks of life.  It is also common for some children to have it the first 6 to 9 months of life, but it may last much longer.
Despite the common name "cradle cap," this condition can affect children on other areas of the body aside from the head. This condition can occur on the face, neck, and ears as well.  It can also occur on the groin and the armpits.