Hair Loss

Differential Diagnosis

Common Diagnoses

Occasional Diagnoses

Rare Diagnoses

  • Secondary Syphilis
  • Trichotillomania
  • Morphoea
  • Malnutrition

Ready Reckoner

Key distinguishing features of the most common diagnoses

AndrogenicSeborrhoeic DermatitisAlopecia AreataAllergic DermatitisTinea Capitis
Normal ScalpYesNoYesNoNo
Abnormal Skin on BodyNoPossibleNoPossiblePossible
Exclamation Mark HairsNoNoYesNoNo
Patchy Hair ThinningYes (M) No (F)YesYesYesYes
Scaling and WeepingNoYesNoPossibleYes

Possible Investigations


Possible:Wood’s light test, hair and scales for mycology.

Small Print:FBC, ESR/CRP, U&E, TFT, FSH/LH, prolactin, autoimmune tests, syphilis serology.

  • Microsporum infections will fluoresce green under a Wood’s (UV) light.
  • Send scrapings and hair for mycology if the scalp looks abnormal.
  • FBC, ESR/CRP and autoimmune tests may help identify autoimmune causes, e.g. SLE.
  • Syphilis serology: Old-fashioned, but syphilis is on the increase.
  • U&E, TFT, FSH/LH, prolactin will effectively screen for endocrinopathy.

Top Tips

  • Alopecia areata is occasionally associated with other autoimmune diseases. Further assessment is sensible, even at a later consultation.
  • Remember that in telogen effluvium, the traumatic event – such as a significant illness or childbirth – will have taken place about 4 months before the onset of hair loss, so the connection is unlikely to be made by the patient.
  • The patient invariably fears total hair loss – ensure that this is broached and that a realistic prognosis is given.
  • Lymphadenopathy in association with alopecia may suggest an infective process – consider bacterial folliculitis.

Red Flags

  • Alopecia areata has a particularly poor prognosis if there are several patches, there is loss of eyebrows or eyelashes, or if it begins in childhood.
  • Scarring alopecia should prompt the clinician to look for general signs of lupus erythematosus.
  • Trichotillomania in children is usually simply due to habit; in adults, though, it is more often a sign of significant psychological disturbance.
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