Skin Lesions

Lesions are zones (areas) of tissue whose function is impaired due to damage, usually caused by either disease or wounding.

Secondary Lesions such as crusts and scars are derived from Primary Lesions, such as abscesses, ulcers, and tumours. There are many different terms (words) used to describe the different forms of skin lesions.

The following also appear in the glossary section and are included here for reference as a single list.


An abscess is collection of pus surrounded (walled-off) by damaged and inflamed tissue.

An abscess can occur anywhere on the body. An example of an abscess on the skin is a boil - which is caused by the bacterium staphylococcus aureus.


The word 'cicatrix' is the medical term for what is commonly referred to as a 'scar'.

That is, it refers to a variety of dermal and epidermal changes associated with wound healing and resulting in fibrous tissue replacing normal tissue in the affected areas.

The adjective associated with 'cicatrix' is 'cicatricial'.

Atrophy (Skin)

Atrophy is the wasting away of normally developed tissue (which may be forming an organ such as the skin) due to cell degeneration. Atrophy of tissue can occur for various reasons, including - for example, ageing, disuse, or undernourishment.


Crust (in the context of dermatological lesions) refers to an accumulation of:

  • serum,
  • blood, and
  • purulent exudate - which is a pus-like liquid that has seeped through the walls of intact blood vessels (usually as a result of inflammation).


A cyst is an abnormal sac or closed cavity lined with epithelial tissue cells and filled with liquid, or semi-solid matter.

Different types of cyst occur in different parts of the body.


In medicine (incl. dermatology), the word "erosion" refers to the eating away of surface tissue by chemical or physical processes, such as inflammation.

Dermatological erosion is also defined as loss of epidermis above the basal (deepest) layer of the epidermis (outer-layer) of the skin, leaving denuded the outer surface of the skin.

Erosion of the skin is a superficial form of ulceration and usually heals quite readily. The other medical definition of the word erosion is concerned with the loss of surface tooth substance in dentistry.


Excoriation is the destruction or removal of the surface of the skin (or the tissue covering an organ). This may be caused by scratching, scraping, or chemicals. In cases in which excoriation results from the skin being scratched by the patient due to the irritation of the skin, linear crusts and erosions may result. (This can happen when, for example, the patient has scratched itching eczema or dermatitis while asleep.)


Lesions are zones (areas) of tissue whose function is impaired due to damage, usually caused by either disease or wounding. Secondary Lesions such as crusts and scars are derived from Primary Lesions, such as abscesses, ulcers, and tumours.


The word 'lichenification' can have two similar meanings in the context of skin lesions.

It can refer to either of:

  1. Thickening of the epidermis of the skin, such that the normal creases appear to be exaggerated. This may be caused by abnormal / excessive scratching or rubbing of the affected area.
  2. Skin that is marked by the presence of many fine papules.


A macule is a flat circumscribed area of skin of altered skin colour (relative to other skin of the same person). Macules are not elevated above or depressed below the level of surrounding skin, unlike - for example, papules - which are elevated above surrounding skin.


A nodule (on the skin) is a small swelling or aggregation of cells foming a palpable lesion of size in range 0.5 cm - 2 cm in diameter. It may be located in the epidermis, dermis, or subcutaneous layers of the skin. In the cases of some skin conditions, many nodules may be present.


A papule is a small raised spot on the skin that takes the form of a solid palpable lesion of up to
0.5 cm diameter that is elevated above the level of the surrounding skin.

Plaque (Skin)

In the context of the skin (as opposed to its other meaning in dentistry), the word "plaque" refers to a raised lesion whose surface area is much larger than its elevation above the surface of the surrounding skin. This area is usually formed by many papules enlarging or coalescing to form a total area of greater than 2 cm in diameter - though the shape of the area is not necessarily circular, it can take any shape.


Poikiloderma is a condition in which skin begins to waste away (atrophy) and becomes pigmented.

Poikilodremema is also defined (more technically) as a combination of atrophy, hypo- and hyper-pigmented, and telangiectasis. The result is skin of a mottled discolouration/appearance.


Purpura is a type of skin rash that can be considered both as a skin condition, and also as a type of skin lesion. This form of rash results from blood seeping into the skin from small blood vessels called capillaries. The appearance of this rash consists of individual purple spots called petechiae.

Possible causes of purpura include defects in the capillaries and/or deficiency of blood platelets.


A pustule is a small blister on the skin that contains pus.

A pustule is a type of abscess , which usually forms in the dermis or subcutis layers of the skin.


In the context of human dermatology the word 'scale' is used to refer to flakes of dead epidermal cells shed by the skin. More specifically, scale consists of the heaping-up of keratin in the stratum corneum of the skin.


The word 'scar' is commonly used to refer to a variety of dermal and epidermal changes associated with wound healing and resulting in fibrous tissue replacing normal tissue in the affected areas.

The medical term used to refer to scarring is 'cicatrix', or 'cicatricial' (adjective).


Sclerosis is the hardening or 'induration' of skin.

Common causes of sclerosis include scarring following inflammation (which is also known as fibrosis), and / or ageing. Note that sclerosis is not only a skin lesion / condition. Sclerosis can affect different areas of the body, its effects being determined by the area affected and to what extent.


A telangiectasis (the singular noun) is a localized group of distended blood capillary vessels.

It appears as a red spot that may look spidery and that blanches when pressure is applied to the telangiectasis directly. (Plural: Telangiectases.)


A skin ulcer is a break in the skin such that there is a loss of the epidermis and part or all of the dermis of the skin, leaving a moist depressed lesion.

There are many types of skin ulcer. There are also ulcers that affect other parts of the body.


A vesicle is a very small blister in the skin that contains a clear liquid called serum.

The sizes of vesicles range from less than 0.1 cm to a maximum of 0.5 cm in diameter.

Vesicles occur in several skin disorders, including eczema and herpes.


Wheals are rounded or flat-topped elevated lesions caused by broad flares of swollen skin containing an excessive accumulation of fluid. The medical term for 'swollen with an excessive accumulation of fluid' is 'edematous', although this word is not used in all textbooks.

A 'wheal' or 'weal' is also known as a 'hive'. These are commonly used, i.e. non-medical, words for the feature whose medical name is know as 'urticaria' (plural). However, 'urticaria' are the result of an allergic reaction and the release of histamine. Although this is usually transitory, it can constitute a medical emergency if the lips, eyes, or tongue are affected because considerable swelling can occur.

See also the pages about the structure of skin, skin disorders and skin pigmentation conditions.

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