Since birth, this 5-month-old boy has had a facial rash that comes and goes. At times severe, it is the source of much familial disagreement about its cause: Some say the problem is related to food, while others are sure it represents infection.
Several medications, including triple-antibiotic ointment and nystatin cream, have been tried. None have had much effect.
The child is well in all other respects—gaining weight as expected and experiencing normal growth and development. The rash does not appear to bother him as much as it bothers his family to see.
Further questioning reveals a strong family history of seasonal allergies, eczema, and asthma. Notably, all affected individuals have long since outgrown those problems.
The child is in no apparent distress but is noted to have nasal congestion, with continual mouth breathing. Overall, his skin is quite dry and fair.
The rash itself is rather florid, affecting the perioral area and spreading onto the cheeks in a symmetrical configuration. The skin in these areas is focally erythematous, though not swollen. It is also quite scaly in places, giving the appearance of, as his parents note, “chapped” skin. Examination of the diaper area reveals a similar look focally.
What’s the diagnosis?