What are Lesions?

A lesion is any abnormality in the tissue of an organism (in layman’s terms “damage”), usually caused by disease or trauma.

There are many common causes of skin lesions. The most common cause of a skin lesion is an infection on or in the skin. One example is a wart. The wart virus is passed from one person to another through direct skin-to-skin contact.

Teenagers may have skin lesions from acne, while aging may bring freckles, moles and discoloration. A number of infectious diseases cause rashes, and itchy hives or rashes may accompany allergic reactions. Skin changes can also occur with chronic conditions, such as diabetes or autoimmune disorders. Skin lesions, such as boils and carbuncles, may also be caused by local infections of the skin or hair follicles.

A systemic infection, an infection that occurs throughout your body, such as chicken pox or shingles, can cause skin lesions all over your body.

Some skin lesions are hereditary, such as moles and freckles. Birthmarks are lesions that exist at the time of birth.

Others can be the result of an allergic reaction or sensitivity caused by conditions like poor circulation or diabetes.

Skin Lesions are classified into three main groups.

Primary lesions

An initial alteration in the skin.  A primarily lesion is directly associated with the disease process.  Identifying the primary lesion, is the first step towards identification of the disease or cutaneous process. Primary lesions include the maculepapulepustulesnodulesvesiclebullanoduletumorwheal


A circumscribed flat area less than 1 cm of discoloration without elevation or depression of surface relative to surrounding skin.


A papule is an elevated, solid lesion, less than 1cm.  Often inflamed and tender but papules do not contain pus but may develop into a pustule.


A pustule often arises from a papule and is an inflamed raised blemish containing pus.  Pustules are a primary lesion of acne vulgaris.


A palpable, solid lesion, greater than 1 cm in diameter.  These are usually found in the dermal or subcutaneous tissue, and the lesion may be above, level with, or below the skin surface.


Cysts are closed fluid filled sacs which may be found under the skin or in the other parts of the body.  Sebaceous cysts in the skin contain sebum and are not infected.

Vesicles and Bullae (Bullus – Singular)

A vesicle is a small, superficial elevationof the skin, less than 0.5cm, that contains serous fluid – a small blister.

A Bullus is a raised lesion greater than 0.5cm that contains serous fluid – a larger blister.


Tumors are solid, firm lesions typically larger than 2cm diameter, which represent an overgrowth, or proliferation of skin cells.  They can be above, level with, or beneath the skin surface.  Also known as a mass.  They may be malignant or benign.


A wheals is a transient elevated papule or plaque, often with erythematous borders and pale centers.  E.g. Hive

Secondary Lesions

Formed from the primary lesion worsening in some way

A secondary lesion is a modification or development of a primary lesion into further stage of a disease or condition.  This can be due to traumatic injury, natural progression from primary lesion in the disease manifestation process or other external factors.

Secondary lesions include Scale, Crust, Scab, Erosion, Ulcer, Fissure, Atrophy and Lichenification.


A scales is formed when epidermal cells are produced by abnormal keratinasation of the skin which have died and then been shed.  E.g. scales form on plaques of psoriasis.

Crust and Scabs

A crust is a dried collection of blood serum or plasma and the breakdown of cellular matter which has exuded onto the skin surface.

A scb forms from an open, bleeding wound where the blood cells have collected and dried within the fibrin mesh formed by the action of the platelets in the blood clotting process.

Atrophy (Depression Scar)

Atrophy means ‘wasting away’ and causes the thinning in the epidermis/dermis which in turn leads to depression of the skin.  E.g. Acne scar , chicken pox scar.

Skin Erosion

An erosion is the term given to a superficial destruction of the epidermis down to the basement membrane at the dermal-epidermal junction leaving moist and oozing tissue prone to infection.  Superficial erosions can develop into deeper ulcers.


An ulcer is a wound to the skin or to a mucous membrane which cause the ongoing disintegration of the skin and reluctance to heal.

Ulcers can be result of trauma, continual pressure infection or can be due to underlying health issues such as diabetes.


A fissure is a split or crack in the skin tissue that extends into dermis and area common characterisitic of extremely dry skin conditions such as eczema.

Fissures can develop from a primary lesion or form as a result of trauma, scratching or infection.


Lichenification is the term to describe the thickening of the epidermis which may be caused by scratching.  E.g. Eczema , Contact dermatitis

Tertiary Lesions

Only occur with serious disease after Primary & Secondary

Treating Skin Lesions

Treatment of dermal lesions will depend heavily on the type and cause of the lesion. Treatments range from topical applications for less severe cases, to oral medications in the case of systemic infections. In some cases, surgical removal of the lesion may be required, which is often accomplished either by Short Wave Diathermy / ThermolysisCryotherapy, or laser therapy.