A papule is a rounded or oval hard elevation of the skin, varying in size from a pinhead to a pea. Early, it has a feeling similar to that of fine shot beneath the skin. It is usually reddish when fully developed. Warts and pimples are examples. Papules are the characteristic eruption in the first stage of variola.

A vesicle is a slight circumscribed elevation of the skin containing a clear or opaque fluid or serum. It usually follows the papular stage of an eruption and is found in allergic contact dermatitis, herpes, and the second stage of smallpox.

A pustule is an elevation of the skin containing pus, about the size of a vesicle. It often follows the vesicular stage in an eruption. A pustule is produced by suppuration of serum contained in a vesicle, giving it a smoky or cloudy appearance. It is found in impetigo, boils, acne, deep fungus infections, and the third stage of smallpox.

A herpic eruption consists of a series of minute vesicles situated upon a red hard base attended by a burning or smarting pain. When occurring on the lips, it is called herpes labialis. When occurring on the nose, it is called herpes nasi; around the ribs, herpes zoster (shingles); and in the genital area, it is known as herpes progenitalis.

These blister-like eruptions are large elevations of the skin containing a clear or opaque fluid. The large vesicles vary in size from a pea to a goose egg.

Wheals (pomphi) are circumscribed areas of cutaneous or subcutaneous edema of a temporary character. They are common in allergic reactions from drugs, insect bites, or an environmental irritant such as sunlight, pressure, heat or cold.

A macule is an area of discoloration without elevation or depression. It may be any color, shape, or size. Macules that occur in the eruptive fevers are red and slightly elevated above the skin level due to hyperemia. They measure 2--4 mm in diameter, may appear upon any skin surface, and may be distributed sparsely or densely. They are characteristic of measles, freckles, and flat moles.

Nodules are solid, usually elevated, lesions of the skin of deep origin which vary in size from a pea to a cherry. A nodule is essentially a small tumor.

Cutaneous or subcutaneous hemorrhages may occur as small spots called petechiae or in large areas called ecchymoses. They occur as an eruptive sign in cerebrospinal meningitis and dengue and are also commonly found in scurvy, purpura, and hemophilia. They are produced from a lack of motor function being expressed in the minute muscular fibers forming the blood vessel walls, permitting them to relax, fibers to separate, and blood to ooze between the minute fibers.

This is an evenly distributed redness of the skin due to a cutaneous hyperemia such as seen in erysipelas and the exanthemata. The eruption presents an uneven redness.

This condition is the result of dilated superficial blood vessels. Most lesions are of unknown cause, but they may be associated with certain systemic disorders (eg, iatrogenic).

An abscess is a collection of pus circumscribed by a pyogenic membrane and located in the subcutaneous tissue. Abscesses of the skin usually develop suddenly and are small in size except when on the scalp. They form round swellings that are hard or firm at first, but soon become soft and fluctuate under pressure. When opened, they give off a thick pus. They are most common on the scalp with eczema, on the face and neck with acne, and on the extremities with scabies. They may disappear by absorption or open of their own accord. There is but slight pain and discomfort in cutaneous abscesses. They differ from a boil in that they are not raised and pointed, do not have a central core, and are less firm. They differ from carbuncles by the absence of constitutional symptoms, brawny infiltration, intense inflammation, and cubiform mode of opening. An abscess differs from syphilitic gumma in that a gumma has no pain, is dark red in color, grows slowly, is usually multiple, and when cut, it gives off little bloody fluid.

Boils may be classed as a form of cutaneous eruption. They are circumscribed areas of suppuration in the subcutaneous tissue and usually involve one or more sebaceous glands. At the onset, they are red; but as soon as suppuration has occurred, they become yellowish-white.

Tumors are atypical growths of various size, shape, and consistency located in the deep layers of the skin.

This is a scar or a similar effect of nature to heal skin damage by means of connective tissue. It occurs only where the papillary layer of the skin is destroyed.

This term refers to a thickening of the skin associated with accentuated skin markings.

A scab is a dried secretion or exudate (eg, blood, pus, serum) upon the skin which follows vesicles, pustules, weeping eczema, other inflammatory and infectious diseases, cuts and abrasions.

This is a circumscribed, light in color, thin layer of epidermal cells that has become detached and is about to shed. Scales are common in psoriasis, superficial fungus infections, and chronic dermatitis.

Excoriation refers to a scratch mark or a superficial denudation of the skin.

A fissure is a crack in the skin extending down to the corium and usually located in the folds of the skin over the joints.

The term erosion refers to a loss of epidermal tissue such as seen in herpes infection.

An ulcer is a deep erosion where epidermal tissue and at least part of the dermal tissue is lost. Ulcers often result from acute bacterial infection, physical trauma, peripheral vascular disease, and chronic fungal infections.