Itchy Scalp
Differential Diagnosis
Common Diagnoses
- Head Lice
- Seborrhoeic Eczema
- Psoriasis
- Lichen Simplex
- Impetigo (May be Underlying Head Lice or Eczema)
Occasional Diagnoses
- Allergic/Contact Eczema
- Other Fungal Infections
Rare Diagnoses
- Stress/Depression
- Viral Infection (e.g. Chickenpox – a Common Problem but only Rarely Presents with Scalp Itch)
Ready Reckoner
Key distinguishing features of the most common diagnoses
| Head Lice | Seborrhoeic Eczema | Psoriasis | Lichen Simplex | Impetigo | |
|---|---|---|---|---|---|
| Scaly Scalp | No | Yes | Yes | Possible | No |
| Pustular Lesions | Possible | No | No | No | Yes |
| Skin Lesions Elsewhere | No | Possible | Possible | Possible | Possible |
| Visible Egg Cases | Yes | No | No | No | No |
| Chronic Problem | No | Possible | Yes | Possible | No |
Possible Investigations
- It is highly unlikely that any investigations will be required at all. Confirmation of a fungal infection may be obtained via fluorescence under a Wood’s light or by microscopy and culture of scalp and hair samples.
Top Tips
- Whatever the actual diagnosis, scratching will perpetuate or complicate the problem and so should be discouraged.
- Consider examining the skin and nails, as these may provide useful additional clues.
- The diagnosis in a child is very likely to be head lice; the list of differentials increases the older the patient.
Red Flags
- Scalp impetigo in a child – particularly if it relapses rapidly – suggests an underlying problem such as head lice or eczema. This needs treating too, or the symptom will persist.
- In an otherwise puzzling case, consider psychological causes – stress and depression can sometimes present with scalp itching.