Overview
Alopecia means “loss of hair“.
Hair grows in small clusters of 3-4 hairs per follicle unit. Hair grows through 3 phases. Follicles can move through this process and back again based on hormonal signalling. Normally, an individual loses about 50 – 100 hairs per day.
Phases of hair growth
| Phase of hair growth | Description | Duration |
|---|---|---|
| Anagen | The main period of hair growth. Old hair is shed, and new hair starts to grow. 92 % of hairs are in anagen at any time. | 3 – 6 years |
| Catagen | Slowing down or starting up | 2 – 3 weeks |
| Telogen | Hair that is not currently growing (resting phase) | 3 – 4 m |
- Signs of abnormal hair loss
- Hair on the pillow in the morning
- Clogged drain after a shower
Classification of alopecia
| Types of alopecia | Examples |
|---|---|
| Primary cicatricial (scarring) alopecia | Lichen planopilaris, discoid lupus |
| Secondary cicatricial (scarring) alopecia | Fungal infection, sarcoidosis, metastatic cancer, burns |
| Primary non-scarring alopecia | Anagen effluvium, telogen effluvium, androgenic alopecia, alopecia areata, trichotillomania, traction alopecia, and non-inflammatory tinea capitis |
| Secondary non-scarring alopecia | SLE, secondary syphilis, hypothyroidism, hyperthyroidism, hypopituitarism |
