Facial Rash
Unlike most of the other ‘skin’ sections, this section is presented according to the rash distribution. This is because it is a common presentation, one with a wide differential and one which causes the patient significant concern, largely because of the cosmetic impact. Occasionally, it can be caused by, or represent, significant pathology. Individual facial spots – such as basal cell carcinoma – aren’t considered here.
Differential diagnosis
Common Diagnoses
- Acne
- Rosacea
- Seborrhoeic Eczema
- Impetigo
- Perioral Dermatitis
Occasional Diagnoses
- Chloasma
- Sycosis Barbae
- Drug Side Effect: Especially Phototoxicity
- Infection (e.g. Herpes Zoster and Simplex, Cellulitis, Chickenpox, Slapped Cheek)
- Allergic Eczema
- Acne Excoriée
- Post Inflammatory Hypo- or Hyperpigmentation
- Pityriasis Alba
- Petechiae from Coughing/Vomiting/Straining
- Other Generalised Skin Diseases (e.g. Psoriasis, Vitiligo)
Rare Diagnoses
- Stevens–Johnson Syndrome
- SLE
- Mitral Flush
- Tuberous Sclerosis
- Lupus Vulgaris
- Sarcoidosis
- Dermatomyositis
Ready reckoner
Key distinguishing features of the most common diagnoses
| Acne | Rosacea | Seborrhoeic Eczema | Impetigo | Perioral Dermatitis | |
|---|---|---|---|---|---|
| Mainly Around Mouth | Possible | No | No | Possible | Yes |
| Rash Elsewhere | Possible | No | Possible | Possible | No |
| Age >40 | No | Yes | Possible | Possible | Possible |
| Papules and Pustules | Yes | Yes | No | Possible | Yes |
| Rapid Response to Antibiotics | No | Yes | No | Yes | Yes |
Possible investigations
Likely: None.
Possible: FBC, ESR/CRP, autoantibody screen, CPK.
Small Print: Viral or bacterial swabs, skin biopsy, muscle biopsy.
- FBC: WCC raised in any infection; may be normochromic, normocytic anaemia in SLE.
- ESR/CRP, autoantibody screen: ESR/CRP likely to be raised in infection and SLE; autoantibodies may be positive in the latter.
- CPK: Elevated in dermatomyositis.
- Viral or bacterial swabs: To help diagnosis in obscure cases or if secondary infection suspected.
- Skin biopsy; muscle biopsy: The former for suspected lupus vulgaris or sarcoidosis; the latter to confirm dermatomyositis.
Top Tips
- Do not underestimate the possible impact of a facial rash on a patient’s life. The cosmetic effect may be devastating.
- A therapeutic trial of antibiotics in acne may take up to 3 months to take effect – ensure the patient is aware of this.
- Remember that impetigo may simply represent superinfection of an underlying skin problem, such as eczema, which will require treatment in its own right.
- Check on OTC medication usage. In particular, remember that hydrocortisone 1% cream is available over the counter – inappropriate use might aggravate rosacea and perioral dermatitis.
- Parents are sensitised to non blanching rashes. They can be reassured that such a rash restricted to the face (indeed, restricted to the entire distribution of the superior vena cava) is not due to meningitis.
Red Flags
- A complaint of dramatic facial ‘sunburn’ in the elderly may well represent a phototoxic reaction – check the drug history.
- Beware the acute onset of unilateral unexplained facial erythema with mild oedema, especially in an elderly patient. This may well be the start of cellulitis or herpes zoster.
- Warn patients with facial zoster or herpes simplex infection near the eye to report any ocular problems.
- Acne excoriée may be a marker of significant psychiatric pathology.