Overview
Also known as seborrhoeic eczema, seborrhoeic dermatitis is a relatively common inflammatory skin condition that occurs in areas that have a lot of sebaceous glands (the scalp, nasolabial folds, ears, eyebrows, chest, flexures, and skin folds). ‘Seborrhoeic’ means excessively oily or greasy.
In infants, seborrhoeic dermatitis tends to occur within the first 6 weeks of life and commonly affects the scalp (known as ‘cradle cap’), nappy area, face, and limb flexures.
Pathophysiology
The cause of seborrhoeic dermatitis is unknown, however, it is thought to be related to hormones, as it can arise in infancy, disappear in childhood, and then reappear during adolescence as sex hormones stimulate sebaceous glands. It is also thought that the Malassezia furfur fungus colonises sebum-rich areas, proliferates, and induces local inflammatory responses.
Epidemiology
- The incidence of seborrhoeic dermatitis is highest in infants <3 months old, during adolescence, and in adults aged 30-60 years
- This may be due to hormonal changes as mentioned above
Diagnosis
Presentation
Seborrhoeic dermatitis in infants tends to present in the 8 weeks of life and resolves by 6-12 months. Its features include:
- ‘Cradle cap’ – most common presentation, but also may affect face, neck, ears, or skin flexures:
- Yellow-brown, large, greasy scales appear on the scalp in cradle cap
- The rash tends to be well-defined but can be confluent
- Itching is relatively mild and the infant is usually well – sleep is usually unaffected
Diagnosis
Diagnosis is usually clinical if the history is clear and there are no features of suspected underlying causes present (such as tinea capitis, psoriasis, atopic eczema, or HIV).
Differential Diagnoses
Atopic dermatitis
- Itching is more of a prominent feature and can cause distress and interrupt sleep
- The face, scalp, trunk, and extensor surfaces of the limbs tend to be affected
- The nappy area is usually spared, whereas, in seborrhoeic dermatitis, the nappy area may also be affected
- There may be a history of atopy
Psoriasis
- The rash appears as well-circumscribed plaques with silvery scales
- Nail pitting may be seen
- The rash tends to be found on the extensor surfaces of the knees and elbows
Allergic contact dermatitis
- Eczematous rashes tend to be localised to a specific area after exposure to a certain allergen
- Signs and symptoms tend to occur 24-72 hours after exposure due to allergic contact dermatitis being a delayed-type hypersensitivity reaction
Pityriasis rosea
- There is often a herald patch followed by erythematous, scaly, oval patches over the trunk similar in appearance to a ‘fir tree’ and tend to be less widely distributed
- There may be a history of a recent viral infection
Pityriasis versicolor
- Tends to cause flatter, less widely-distributed lesions that may be hypopigmented, pink, or brown
- Often noticed after a holiday when the person has been exposed to the sun
Scabies
- Severe, acute itching
- Burrows may be seen
- Household members or close contacts may also be affected
Management
Overview
In infants, seborrhoeic dermatitis tends to resolve by around 6-12 months of age. In most cases, reassurance and simple measures such as softening scales with emollients, gentle brushing to loosen scales, and washing with baby shampoo are sufficient.
Imidazole cream may be used if initial measures are unsuccessful.
If symptoms persist for >4 weeks with treatment, seek specialist advice.
Complications
- Secondary infection
- Erythroderma – rare
Prognosis
- In infants, seborrhoeic dermatitis tends to resolve by around 6-12 months of age
