Merck Manual

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Description of Skin Lesions


Julia Benedetti

, MD, Harvard Medical School

Reviewed/Revised Dec 2021 | Modified Sep 2022
Topic Resources

An extensive language has been developed to standardize the description of skin lesions, including

Rash is a general term for a temporary skin eruption.

Cross-section of the skin and skin structures

Cross-section of the skin and skin structures

Lesion Type (Primary Morphology)

Macules are flat, nonpalpable lesions usually < 10 mm in diameter. Macules represent a change in color and are not raised or depressed compared to the skin surface. A patch is a large macule. Examples include freckles, flat moles, tattoos, and port-wine stains Capillary Malformations Capillary malformations are present at birth and appear as flat, pink, red, or purplish lesions. Port-wine stains are capillary vascular malformations that are present at birth and that manifest... read more Capillary Malformations , and the rashes of rickettsial infections Overview of Rickettsial and Related Infections Rickettsial diseases (rickettsioses) and related diseases (anaplasmosis, ehrlichiosis, Q fever, scrub typhus) are caused by a group of gram-negative, obligately intracellular coccobacilli. All... read more Overview of Rickettsial and Related Infections , rubella Rubella (See also Congenital Rubella.) Rubella is a viral infection that may cause adenopathy, rash, and sometimes constitutional symptoms, which are usually mild and brief. Infection during early pregnancy... read more Rubella , measles Measles Measles is a highly contagious viral infection that is most common among children. It is characterized by fever, cough, coryza, conjunctivitis, an enanthem (Koplik spots) on the oral mucosa... read more Measles (can also have papules and plaques), and some allergic drug eruptions Drug Eruptions and Reactions Drugs can cause multiple skin eruptions and reactions. The most serious of these are discussed elsewhere in THE MANUAL and include Stevens-Johnson syndrome and toxic epidermal necrolysis, hypersensitivity... read more Drug Eruptions and Reactions .

Papules are elevated lesions usually < 10 mm in diameter that can be felt or palpated. Examples include nevi, warts, lichen planus Lichen Planus Lichen planus is a recurrent, pruritic, inflammatory eruption characterized by small, discrete, polygonal, flat-topped, violaceous papules that may coalesce into rough scaly plaques, often accompanied... read more Lichen Planus , insect bites, seborrheic keratoses Seborrheic Keratoses Seborrheic keratoses are superficial, often pigmented, epithelial lesions that are usually verrucous but may occur as smooth papules. The cause of seborrheic keratosis is unknown, but genetic... read more Seborrheic Keratoses , actinic keratoses Actinic keratoses Chronic affects of sunlight include photoaging, actinic keratoses, and skin cancer. (See also Overview of Effects of Sunlight.) Chronic exposure to sunlight ages the skin (photoaging, dermatoheliosis... read more Actinic keratoses , some lesions of acne Acne Vulgaris Acne vulgaris is the formation of comedones, papules, pustules, nodules, and/or cysts as a result of obstruction and inflammation of pilosebaceous units (hair follicles and their accompanying... read more Acne Vulgaris , and skin cancers Overview of Skin Cancer Skin cancer is the most common type of cancer and commonly develops in sun-exposed areas of skin. The incidence is highest among outdoor workers, sportsmen, and sunbathers and is inversely related... read more . The term maculopapular is often loosely and improperly used to describe many red rashes; because this term is nonspecific and easily misused, it should be avoided.

Pustules are vesicles that contain pus. Pustules are common in bacterial infections and folliculitis and may arise in some inflammatory disorders including pustular psoriasis Subtypes of Psoriasis Subtypes of Psoriasis .

Urticaria Urticaria Urticaria consists of migratory, well-circumscribed, erythematous, pruritic plaques on the skin. Urticaria also may be accompanied by angioedema, which results from mast cell and basophil activation... read more Urticaria (wheals or hives) is characterized by elevated lesions caused by localized edema. Wheals are pruritic and red. Wheals are a common manifestation of hypersensitivity to drugs, stings or bites, autoimmunity, and, less commonly, physical stimuli including temperature, pressure, and sunlight. The typical wheal lasts < 24 hours.

Erosions are open areas of skin that result from loss of part or all of the epidermis. Erosions can be traumatic or can occur with various inflammatory or infectious skin diseases. An excoriation is a linear erosion caused by scratching, rubbing, or picking.

Purpura is a larger area of hemorrhage that may be palpable. Palpable purpura is considered the hallmark of leukocytoclastic vasculitis. Purpura may indicate a coagulopathy. Large areas of purpura may be called ecchymoses or, colloquially, bruises.

Scars are areas of fibrosis that replace normal skin after injury. Some scars become hypertrophic or thickened and raised. Keloids Keloids Keloids are smooth overgrowths of fibroblastic tissue that arise in an area of injury (eg, lacerations, surgical scars, truncal acne) or, occasionally, spontaneously. Keloids are more frequent... read more Keloids are hypertrophic scars that extend beyond the original wound margin.

Lesion Configuration (Secondary Morphology)

Configuration is the shape of single lesions and the arrangement of clusters of lesions.

Linear lesions take on the shape of a straight line and are suggestive of some forms of contact dermatitis Contact Dermatitis Contact dermatitis is inflammation of the skin caused by direct contact with irritants (irritant contact dermatitis) or allergens (allergic contact dermatitis). Symptoms include pruritus and... read more Contact Dermatitis , linear epidermal nevi, and lichen striatus. Excoriations resulting from scratching are typically linear.

Reticulated lesions have a lacy or networked pattern. Examples include cutis marmorata and livedo reticularis.

Texture of Skin Lesions

Some skin lesions have visible or palpable texture that suggests a diagnosis.

Lichenification is thickening of the skin with accentuation of normal skin markings; it results from repeated scratching or rubbing.

Induration, or deep thickening of the skin, can result from edema, inflammation, or infiltration, including by cancer. Indurated skin has a hard, resistant feeling. Induration is characteristic of panniculitis Panniculitis Panniculitis describes inflammation of the subcutaneous fat that can result from multiple causes. Diagnosis is by clinical evaluation and biopsy. Treatment depends on the cause. (See also Erythema... read more Panniculitis , some skin infections, and cutaneous metastatic cancers.

Xanthomas, which are yellowish, waxy lesions, may be idiopathic or may occur in patients who have lipid disorders.

Location and Distribution of Skin Lesions

It is important to note whether

  • Lesions are single or multiple.

  • Particular body parts are affected (eg, palms or soles, scalp, mucosal membranes).

  • Distribution is random or patterned, symmetric or asymmetric.

  • Lesions are on sun-exposed or protected skin.

Although few patterns are pathognomonic, some are consistent with certain diseases.


When examining the color of skin, health care practitioners should note that the natural color of a patient's skin can change the appearance of colors.

Red skin (erythema) can result from many different inflammatory or infectious diseases. Cutaneous tumors are often pink or red. Superficial vascular lesions such as port-wine stains may appear red.

Orange skin is most often seen in hypercarotenemia, a usually benign condition of carotene deposition after excess dietary ingestion of beta-carotene.

Shades of blue, silver, and gray can result from deposition of drugs or metals in the skin, including minocycline, amiodarone, and silver (argyria). Ischemic skin appears purple to gray in color. Deep dermal nevi appear blue.

Other Clinical Signs of Skin Lesions

Dermatographism (dermographism) is the appearance of an urticarial wheal after focal pressure (eg, stroking or scratching the skin) in the distribution of the pressure. Up to 5% of normal patients may exhibit this sign, which is a form of physical urticaria.

Koebner phenomenon describes the development of lesions within areas of trauma (eg, caused by scratching, rubbing, or injury). Psoriasis frequently exhibits this phenomenon, as may lichen planus Lichen Planus Lichen planus is a recurrent, pruritic, inflammatory eruption characterized by small, discrete, polygonal, flat-topped, violaceous papules that may coalesce into rough scaly plaques, often accompanied... read more Lichen Planus , often resulting in linear lesions.

Drugs Mentioned In This Article

Drug Name Select Trade
Amzeeq, Arestin, Dynacin, Minocin, minolira, Myrac, Solodyn, Ximino, Zilxi
Cordarone, Nexterone, Pacerone
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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