Seborrhoeic Dermatitis

Infantile seborrhoeic dermatitis (ISD) is a common, harmless rash of early infancy. On the scalp it is called cradle cap: greasy white or yellow scales that join into a crust, mostly on the crown and front of the head. It can also affect the eyebrows, the sides of the nose, behind the ears, and skin folds such as the armpits and nappy area (NHS; DermNet). Cradle cap affects about 10% of babies. It is seen from about 3 weeks to 12 months of age and peaks at 3 months (DermNet, Cradle cap 2017). The cause is unclear. Proposed drivers are oil glands still stimulated by the mother’s hormones and the skin yeast Malassezia. It is not contagious (NHS; DermNet). Most cases settle by 6–12 months, so a true seborrhoeic rash is uncommon in the 1–4 age range. DermNet advises that if “cradle cap” persists beyond 12 months, the diagnosis should be reconsidered, and Atopic Dermatitis and Psoriasis are the main alternatives.

Seborrhoeic Dermatitis [relates] Malassezia Seborrhoeic Dermatitis [precedes] Atopic Dermatitis

Telling it apart from atopic eczema. Both conditions can start in the first 8 weeks of life on the scalp and face, so they are hard to separate early on (Napolitano et al., Dermatol Ther 2022). The most useful differences are:

• Itch. ISD is “not itchy or painful and does not bother your baby” (NHS), and DermNet notes that the baby looks undisturbed even when the rash is widespread. AD is intensely itchy, with scratching, poor sleep and irritability (Türe Avcı et al., Children 2026).
• Scale. ISD has oily, yellow, greasy scale. AD is dry and rough and may weep and crust when it flares (Türe Avcı 2026).
• Where it appears. ISD favours the skin folds and the nappy area and armpits, where it shows as salmon-pink, often peeling patches. Infantile AD typically spares the nappy area, groin and armpits and favours the cheeks and the outer surfaces of the limbs (Healio; DermNet, Napkin dermatitis; Siegfried & Hebert, J Clin Med 2015).
• Course. ISD is self-limiting over weeks to months. AD relapses and continues into the toddler years, when it moves to the elbow and knee creases. Dermoscopy can help a clinician: ISD shows patchy dotted vessels with yellowish scale (Türe Avcı 2026). On darker skin, ISD may look less like classic cradle cap and instead show redness, flaking and lighter patches in the folds (DermNet), which can be confused with Pityriasis Alba or with eczema on darker skin. See Eczema in Skin of Colour.

Seborrhoeic Dermatitis [contradicts] Atopic Dermatitis Seborrhoeic Dermatitis [part-of] Differential Diagnosis of Toddler Eczema Seborrhoeic Dermatitis [relates] Eczema in Skin of Colour

Overlap: one disease or two? Some dermatologists question whether ISD is a separate disease at all. In a Greek retrospective cohort of 87 infants with ISD, 30 of the 49 followed up went on to show AD features: 23 developed AD an average of 6.4 months after ISD began, and 7 already had AD features when ISD was diagnosed. The AD rate in the ISD group (34.4%, assuming everyone lost to follow-up recovered) was about three times the local background rate of 10.7% (Alexopoulos et al., Pediatr Dermatol 2014). The authors concluded the two conditions are strongly linked or may lie on the same clinical spectrum. In practice, a baby whose cradle cap is followed by itchy patches on the cheeks or limbs is showing the typical evolution towards AD. The itch, not the scale, is the signal to start an eczema plan.

Conflict: [Alexopoulos et al., Pediatr Dermatol, 2014; Moises-Alfaro et al., Int J Dermatol, 2002] suggest infantile seborrhoeic dermatitis and AD may be clinical variants of the same disease. [Türe Avcı et al., Children, 2026; NHS cradle cap, n.d.; DermNet, 2017] treat ISD as a distinct, non-itchy, self-limiting condition with its own distribution. Unresolved — add to open_questions.

Seborrhoeic Dermatitis [relates] Atopic Dermatitis Seborrhoeic Dermatitis [relates] Atopic March

Management. Most cases need only conservative care (NHS; DermNet):

• Massage an emollient or Coconut Oil into the scalp to loosen the scales, brush gently with a soft brush, then wash with baby shampoo.
• Wash the body with water and an emollient rather than soap. If the nappy area is affected, change nappies promptly and use a barrier cream (see Nappy Rash and Barrier Creams).
• Do not use Olive Oil (NHS says it may not suit the skin), peanut oil (allergy risk; see Peanut Oil Sensitisation), adult shampoos, or fragranced products. Do not pick the crusts, because this raises the risk of infection. For more extensive or stubborn disease, a clinician may prescribe low-potency Hydrocortisone 1% (preferred when the rash is inflamed) or ketoconazole 2% cream for 1–2 weeks (DermNet, Cradle cap). The NHS advises seeing a GP if there is no improvement after a few weeks, if the rash covers the whole body, or if crusts bleed, weep or swell. These can be signs of infection or of atopic eczema or Scabies.

Nut-based oils on an infant scalp

NHS advice is not to use peanut oil for cradle cap because of the allergy risk. Applying food-derived oils to inflamed infant skin may promote sensitisation; see Peanut Oil Sensitisation and Dual-Allergen Exposure Hypothesis.

Emollient Therapy [treats] Seborrhoeic Dermatitis Hydrocortisone [treats] Seborrhoeic Dermatitis Peanut Oil Sensitisation [relates] Seborrhoeic Dermatitis

Connections

• Differential Diagnosis of Toddler Eczema — main infant mimic, source: Healio; Türe Avcı 2026
• Atopic Dermatitis — main differential; ~1 in 3 ISD infants later develop AD, source: Alexopoulos 2014; Napolitano 2022
• Malassezia — implicated skin yeast, target of ketoconazole, source: DermNet 2017
• Nappy Rash — ISD causes salmon-pink fold patches in the nappy area, source: DermNet Napkin dermatitis
• Psoriasis — alternative diagnosis if ‘cradle cap’ persists past 12 months; sebopsoriasis overlap, source: DermNet
• Hydrocortisone — 1% for 1–2 weeks in extensive/inflamed disease, source: DermNet 2017
• Coconut Oil — NHS lists it for loosening scalp scale, source: NHS cradle cap
• Olive Oil — NHS advises against, source: NHS cradle cap
• Peanut Oil Sensitisation — NHS advises against peanut oil, source: NHS cradle cap
• Eczema in Skin of Colour — hypopigmented presentation on darker skin, source: DermNet
• Barrier Creams — for nappy-area involvement, source: NHS cradle cap