A subungual hematoma is a collection of blood (hematoma) underneath a toenail or fingernail (black toenail). It can be extremely painful for an injury of its size, although otherwise it is not a serious medical condition.

Runner's toe is a common condition seen in runners caused by downward pressure or horizontal separation of nail plate from the nail bed. This repetitive traumatic injury leads to bleeding and pooling of blood underneath the nail plate. Clinically, it is characterized by reddish-black discoloration of the toe nail. The nail plate may also become thicker and more brittle as a result of the injury (onychochauxis). Fortunately, the deformed nail plate will gradually grow out and be replaced by new, normal-appearing nail plate in several months time. Infrequently, the toe may become painful and require surgical drainage.

Runner's toe is often associated with malfitting shoes and insufficient space for the toes. Some susceptible runners may also have Morton's toe. In this variant of human foot anatomy, the second toe extends further out than the great toe. The key to prevention of runner's toe is to purchase properly fitted shoes.

The condition also results from a traumatic injury, such as slamming a finger in a door, or from sports activities, such as climbing or hiking rugged terrain. A subungual hematoma that results from the repetitive thrusting of the longest toe into a shoe's toe box is called jogger's toe or runner's toe.

The bleeding comes from the (vascular) nail bed underlying the (avascular) nail plate. A laceration of the nail bed causes bleeding into the constricted area underneath the hard nail plate. Throbbing pain is common. The nail develops a black discoloration overlying the nail bed but under the nail plate.

The presence of bruises may be seen in patients with platelet or coagulation disorders, or those who are being treated with an anticoagulant. Unexplained bruising may be a warning sign of child abuse, domestic abuse, or serious medical problems such as leukemia or meningoccocal infection. Unexplained bruising can also indicate internal bleeding or certain types of cancer. Long-term glucocorticoid therapy can cause easy bruising. Bruising present around the navel (belly button) with severe abdominal pain suggests acute pancreatitis. Connective tissue disorders such as Ehlers-Danlos syndrome may cause relatively easy or spontaneous bruising depending on the severity.

During an autopsy, bruises accompanying abrasions indicate the abrasions occurred while the individual was alive, as opposed to damage incurred post mortem.

The diagnosis is generally a clinical one, with a fluctuant boggy mass developing over the scalp (especially over the occiput) with superficial skin bruising. The swelling develops gradually 12–72 hours after delivery, although it may be noted immediately after delivery in severe cases. The hematoma spreads across the whole calvaria as its growth is insidious and may not be recognized for hours. If enough blood accumulates a visible fluid wave may be seen. Patients can develop raccoon eyes.

Patients with subgaleal hematoma may present with hemorrhagic shock. The swelling may obscure the fontanel and cross suture lines (distinguishing it from cephalohematoma). Watch for significant hyperbilirubinemia. The long-term prognosis is generally good. Laboratory studies consist of a hematocrit evaluation.

A contusion, commonly known as a bruise, is a type of hematoma of tissue in which capillaries and sometimes venules are damaged by trauma, allowing blood to seep, hemorrhage, or extravasate into the surrounding interstitial tissues. The bruise then remains visible until the blood is either absorbed by tissues or cleared by immune system action. Bruises, which do not blanch under pressure, can involve capillaries at the level of skin, subcutaneous tissue, muscle, or bone. Bruises are not to be confused with other similar-looking lesions primarily distinguished by their diameter or causation. These lesions include petechia (1 cm caused by blood dissecting through tissue planes and settled in an area remote from the site of trauma or pathology such as periorbital ecchymosis, e.g.,"raccoon eyes", arising from a basilar skull fracture or from a neuroblastoma).

As a type of hematoma, a bruise is always caused by internal bleeding into the interstitial tissues which does not break through the skin, usually initiated by blunt trauma, which causes damage through physical compression and deceleration forces. Trauma sufficient to cause bruising can occur from a wide variety of situations including accidents, falls, and surgeries. Disease states such as insufficient or malfunctioning platelets, other coagulation deficiencies, or vascular disorders, such as venous blockage associated with severe allergies can lead to the formation of purpura which is not to be confused with trauma-related bruising/contusion. If the trauma is sufficient to break the skin and allow blood to escape the interstitial tissues, the injury is not a bruise but instead a different variety of hemorrhage called bleeding. However, such injuries may be accompanied by bruising elsewhere.

Bruises often induce pain, but small bruises are not normally dangerous alone. Sometimes bruises can be serious, leading to other more life-threatening forms of hematoma, such as when associated with serious injuries, including fractures and more severe internal bleeding. The likelihood and severity of bruising depends on many factors, including type and healthiness of affected tissues. Minor bruises may be easily recognized in people with light skin color by characteristic blue or purple appearance (idiomatically described as "black and blue") in the days following the injury.

Subgaleal hemorrhage or hematoma is bleeding in the potential space between the skull periosteum and the scalp galea aponeurosis.

A hematoma (US spelling) or haematoma (UK spelling) is a localized collection of blood outside the blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillaries. A hematoma is initially in liquid form spread among the tissues including in sacs between tissues where it may coagulate and solidify before blood is reabsorbed into blood vessels. An ecchymosis is a hematoma of the skin larger than 10mm.

They may occur among/within many areas such as skin and other organs, connective tissues, bone, joints and muscle.

A collection of blood (or even a hemorrhage) may be aggravated by anticoagulant medication (blood thinner). Blood seepage and collection of blood may occur if heparin is given via an intramuscular route; to avoid this, heparin must be given intravenously or subcutaneously.

It is not to be confused with hemangioma, which is an abnormal buildup/growth of blood vessels in the skin or internal organs.

Cauliflower ear is an irreversible condition that occurs when the external portion of the ear is hit and develops a blood clot or other collection of fluid under the perichondrium. This separates the cartilage from the overlying perichondrium that supplies its nutrients, causing it to die and resulting in the formation of fibrous tissue in the overlying skin. As a result, the outer ear becomes permanently swollen and deformed, resembling a cauliflower.

The condition is common in martial arts such as boxing, mixed martial arts or wrestling, and in full-contact sports such as rugby union football.

Paroxysmal hand hematoma (also known as "Achenbach syndrome") is a skin condition characterized by spontaneous focal hemorrhage into the palm or the volar surface of a finger, which results in transitory localized pain, followed by rapid swelling and localized blueish discoloration.

Symptoms of a broken nose include bruising, swelling, tenderness, pain, deformity, and/or bleeding of the nose and nasal region of the face. The patient may have difficulty breathing, or excessive nosebleeds (if the nasal mucosa are damaged). The patient may also have bruising around one or both eyes.

The cause is bleeding within the external portion of the ear, a condition known as hematoma auris, perichondrial hematoma, or traumatic auricular hematoma.

Subungual exostoses are bony projections which arise from the dorsal surface of the distal phalanx, most commonly of the hallux.

They tend to be painful due to the pressure applied to the nail bed and plate. They can involve destruction of the nail bed. These lesions are not true osteochondromas, rather it is a reactive cartilage metaplasia. The reason it occurs on the dorsal aspect is because the periosteum is loose dorsally but very tightly adherent volarly.

Subungal malignant melanomas can also occur in canines.

They are distinct from subungual osteochondroma.

The symptoms of a perianal hematoma can present over a short period of time. Pain, varying from mild to severe, will occur as the skin surrounding the rupture expands due to pressure. This pain will usually last even after the blood has clotted, and may continue for two to four days.

Some hematomas are visible under the surface of the skin (commonly called bruises) or possibly felt as masses/lumps. Lumps may be caused by the limitation of the blood to a sac, subcutaneous or intramuscular tissue space isolated by fascial planes. This is a key anatomical feature that helps prevent injuries from causing massive blood loss. In most cases the hematoma such as a sac of blood eventually dissolves; however, in some cases they may continue to grow such as due to blood seepage or show no change. If the sac of blood does not disappear, then it may need to be surgically cleaned out/repaired.

The slow process of reabsorption of hematomas can allow the broken down blood cells and hemoglobin pigment to move in the connective tissue. For example, a patient who injures the base of his thumb might cause a hematoma, which will slowly move all through the finger within a week. Gravity is the main determinant of this process.

Hematomas on articulations can reduce mobility of a member and present roughly the same symptoms as a fracture.

In most cases, movement and exercise of the affected muscle is the best way to introduce the collection back into the blood stream.

A mis-diagnosis of a hematoma in the vertebra can sometimes occur; this is correctly called a hemangioma (buildup of cells) or a benign tumor.

A nasal fracture, commonly referred to as a broken nose, is a fracture of one of the bones of the nose. Symptoms may include bleeding, swelling, bruising, and an inability to breath through the nose. They may be complicated by other facial fractures or a septal hematoma.

The most common causes include assault, trauma during sports, falls, and motor vehicle collisions. Diagnosis is typically based on the signs and symptoms and may occasionally be confirmed by plain X-ray.

Treatment is typically with pain medication and cold compresses. Reduction, if needed, can typically occur after the swelling has come down. Depending on the type of fracture reduction may be closed or open. Outcomes are generally good. Nasal fractures are common, comprising about 40% of facial fractures. Males in their 20s are most commonly affected.

An ecchymosis is a subcutaneous spot of bleeding (from extravasation of blood) with diameter larger than . It is similar to (and sometimes indistinguishable from) a hematoma, commonly called a bruise, though the terms are not interchangeable in careful usage. Specifically, bruises are caused by trauma whereas ecchymoses, which are the same as the spots of purpura except larger, are not "necessarily" caused by trauma, often being caused by pathophysiologic cell function, and some diseases such as Marburg virus disease.

A broader definition of ecchymosis is the escape of blood into the tissues from ruptured blood vessels. The term also applies to the subcutaneous discoloration resulting from seepage of blood within the contused tissue.

Hematomas can be subdivided by size. By definition, ecchymoses are 1 centimeter in size or larger, and are therefore larger than petechiae ( less than 2 millimeters in diameter) or purpura (2 millimeters to 1 centimeter in diameter). Ecchymoses also have a more diffuse border than other purpura.

Melanonychia is a black or brown pigmentation of the normal nail plate, and may be present as a normal finding on many digits in African-Americans, as a result of trauma, systemic disease, or medications, or as a postinflammatory event from such localized events as lichen planus or fixed drug eruption.

There are two types, longitudinal and transverse melanonychia. Longitudinal melanonychia may be a sign of subungual melanoma (acral lentiginous melanoma), although there are other diagnoses such as chronic paronychia, onychomycosis, subungual hematoma, pyogenic granuloma, glomus tumour, subungual verruca, mucous cyst, subungual fibroma, keratoacanthoma, carcinoma of the nail bed, and subungual exostosis.

The primary symptom, hemorrhage, presents differently depending on the degree of injury, with the symptoms of major hemorrhage, shock, abdominal pain, and distention being clinically obvious. Minor hemorrhage often presents as upper left quadrant pain. Patients with unexplained left upper quadrant pain, particularly if there is evidence of hypovolemia or shock, are generally inquired regarding any recent trauma.

Vulvar trauma is more common in prepubertal children due to small labial fat pads and more physical activity. Adults are more protected. Though some injuries are serious, most are accidental minor blunt traumas. The most common type of injury is a straddle injury, which can be incurred through normal activities like bicycle riding. Due to the vascularity of the vulva, it may form a large hematoma when injured. The vulva can also be injured through sexual assault. Vulvar trauma can occur concurrently with vaginal trauma, especially if a sharp object is involved.

An eruption cyst, or eruption hematoma, is a bluish swelling that occurs on the soft tissue over an erupting tooth. It is usually found in children. The fluid in the cyst is sometimes clear creating a pale-coloured cyst although often they are blue. An eruption cyst (eruption hematoma) is a developmental soft-tissue cyst of odontogenic origin that forms over an erupting tooth.

"Distribution" refers to how lesions are localized. They may be confined to a single area (a patch) or may exist in several places. Some distributions correlate with the means by which a given area becomes affected. For example, contact dermatitis correlates with locations where allergen has elicited an allergic immune response. Varicella zoster virus is known to recur (after its initial presentation as chicken pox) as herpes zoster ("shingles"). Chicken pox appears nearly everywhere on the body, but herpes zoster tends to follow one or two dermatomes; for example, the eruptions may appear along the bra line, on either or both sides of the patient.

- Generalized

- Symmetric: one side mirrors the other

- Flexural: on the front of the fingers

- Extensor: on the back of the fingers

- Intertriginous: in an area where two skin areas may touch or rub together

- Morbilliform: resembling measles

- Palmoplantar: on the palm of the hand or bottom of the foot

- Periorificial: around an orifice such as the mouth

- Periungual/subungual: around or under a fingernail or toenail

- Blaschkoid: following the path of Blaschko's lines in the skin

- Photodistributed: in places where sunlight reaches

- Zosteriform or dermatomal: associated with a particular nerve

"Configuration" refers to how lesions are locally grouped ("organized"), which contrasts with how they are distributed (see next section).

- Agminate: in clusters

- Annular or circinate: ring-shaped

- Arciform or arcuate: arc-shaped

- Digitate: with finger-like projections

- Discoid or nummular: round or disc-shaped

- Figurate: with a particular shape

- Guttate: resembling drops

- Gyrate: coiled or spiral-shaped

- Herpetiform: resembling herpes

- Linear

- Mammillated: with rounded, breast-like projections

- Reticular or reticulated: resembling a net

- Serpiginous: with a wavy border

- Stellate: star-shaped

- Targetoid: resembling a bullseye

- Verrucous: wart-like

The primary concern in any splenic trauma is internal hemorrhage, though the exact amount of hemorrhage may be small or large, depending on the nature and degree of injury. Small or minor injuries often heal spontaneously, especially in children. Larger injuries hemorrhage extensively, often causing hemorrhagic shock. A splenic hematoma sometimes ruptures, usually in the first few days, although rupture can occur from hours to even months after injury.