Bluish stain on skin caused by flea/lice bite. Seen especially in case of infestation by pubic louse (pthirus pubis/crab louse.)

Skin lesions are classified into 3 major types. They are:

Primary lesions
Secondary lesions
Special lesions

The primary skin lesions are:

Macule
Patch
Papule
Plaque
Nodule
Vesicle
Bullae
Pustule
Wheal
Cyst

The secondary skin lesion are:

Scale
Crust
Excoriation
Erosion
Ulcer
Fissure
Lichenification
Induration
Sclerosis
Atrophy

The special skin lesions are:

Burrow
Comedone
Telangectasia
Poikiloderma
Milium
Target lesions
Alopecia

Dermatosis refers to ‘skin disease’

Image from http://laporte.uchicago.edu/india2.htm
Favus (latin for ‘honeycomb’ ) is a chronic inflammatory dermatosis affecting the scalp caused by Trichophyton schonleinii.