Erythema nodosum is characterised by nodules (rounded lumps) below the skin surface, usually on the shins. These subcutaneous nodules can appear anywhere on the body, but the most common sites are the shins, arms, thighs, and torso. Each nodule typically disappears after around two weeks, though new one may continue to form for up to six or eight weeks. A new nodule usually appears red and is hot and firm to touch. The redness starts to fade and it gradually becomes softer and smaller until it disappears. Each nodule usually heals completely without scarring over the course of about two weeks. Joint pain and inflammation sometimes continues for several weeks or months after the nodules appear.

Less common variants of erythema nodosum include:

- Ulcerating forms, seen in Crohn's disease

- Erythema contusiforme, when a subcutaneous hemorrhage (bleeding under the skin) occurs with a erythema nodosum lesion, causing the lesion to look like a contusion (bruise)

- Erythema nodosum migrans (also known as subacute nodular migratory panniculitis), a rare form of chronic erythema nodosum characterized by asymmetrical nodules that are mildly tender and migrate over time.

The rings are barely raised and are non-itchy. The face is generally spared.

The first signs of erythema nodosum are often flu-like symptoms such as a fever, cough, malaise, and aching joints. Some people also experience stiffness or swelling in the joints and weight loss.

It occurs in less than 5% of patients with rheumatic fever, but is considered a major Jones criterion when it does occur. The four other major criteria include carditis, polyarthritis, Sydenham's Chorea, and subcutaneous nodules. In this case, it is often associated with Group A streptococcal infection, otherwise known as "Streptococcus pyogenes" infection, which can be detected with an ASO titer.

It is an early feature of rheumatic fever and not pathognomonic of it. It may be associated with mild myocarditis (inflammation of heart muscle). It is also seen in conditions like allergic drug reactions, sepsis and glomerulonephritis.

It often occurs as a harbinger of attacks in hereditary angioedema. In this case it may occur several hours or up to a day before an attack.

Localised discoid lupus erythematosus typically presents with skin lesions localised above the neck, with favoured sites being the scalp, bridge of the nose, cheeks, above the lips and ears as well as the arms hair scratching glasses touching name="Andrews1"/> Another form of discoid lupus erythematosus includes oral discoid. Oral discoid lupus erythematosus results in oral lesions which present themselves as white spots, ulcers and central erythema lesions. Oral discoid lesions most commonly occur on the labial mucosa, vermillion border and buccal mucosa. Atrophy may be observed in some cases. Dentists may be important in establishing the diagnosis before the cutaneous lesions become apparent.

Occurring at any age these lesions appear as raised pink-red ring or bulls-eye marks. They range in size from . The lesions sometimes increase size and spread over time and may not be complete rings but irregular shapes. Distribution is usually on the thighs and legs but can also appear on the upper extremities, areas not exposed to sunlight, trunk or face. Currently EAC is not known to be contagious, but as many cases are incorrectly diagnosed as EAC, it is difficult to be certain.

The condition varies from a mild, self-limited rash (E. multiforme minor) to a severe, life-threatening form known as erythema multiformer major (or erythema multiforme majus) that also involves mucous membranes.

Consensus classification:

- Erythema multiforme minor—typical targets or raised, edematous papules distributed

- Erythema multiforme major—typical targets or raised, edematous papules distributed acrally with involvement of one or more mucous membranes; epidermal detachment involves less than 10% of total body surface area (TBSiA)

- SJS/TEN—widespread blisters predominant on the trunk and face, presenting with erythematous or pruritic macules and one or more mucous membrane erosions; epidermal detachment is less than 10% TBSA for Stevens-Johnson syndrome and 30% or more for toxic epidermal necrolysis.

The mild form usually presents with mildly itchy (but itching can be very severe), pink-red blotches, symmetrically arranged and starting on the extremities. It often takes on the classical "target lesion" appearance, with a pink-red ring around a pale center. Resolution within 7–10 days is the norm.

Individuals with persistent (chronic) erythema multiforme will often have a lesion form at an injury site, e.g. a minor scratch or abrasion, within a week. Irritation or even pressure from clothing will cause the erythema sore to continue to expand along its margins for weeks or months, long after the original sore at the center heals.

The typical rash commonly appears on buttocks. This then resembles the colour of a baboon’s buttocks. Other areas like upper inner thigh and armpits, may be affected by the rash. The rashes are red and well-defined. The presentation is typically symmetrical and not associated with systemic symptoms.

Erythema disappears on finger pressure (blanching), while purpura or bleeding in the skin and pigmentation do not. There is no temperature elevation, unless it is associated with the dilation of arteries in the deeper layer of the skin.

Predisposing factors include abnormal amount of subcutaneous fat, thick ankles and abnormally poor arterial supply. Abnormal arterial supply causes low-grade ischemia of ankle region. The ankle skin becomes sensitive to temperature changes. When weather is cold, ankle is cold, blue and often tender. In hot weather, ankle becomes hot, edematous, swollen and painful. Chilblains may be present. On palpation, small superficial and painful nodules are felt. They break down to form small and multiple ulcers. Fresh crops of nodules appear in periphery of ulcer and ultimately break down. In nodular stage, pain is present; while it subsides in ulcerative stage.

Erythema anulare centrifugum (EAC), also known as deep gyrate erythema, erythema perstans, palpable migrating erythema and superficial gyrate erythema, is a descriptive term for a class of skin lesion presenting redness (erythema) in a ring form ("anulare") that spreads from a center ("centrifugum"). It was first described by Darier in 1916. Many different terms have been used to classify these types of lesions and it is still controversial on what exactly defines EAC. Some of the types include annular erythema (deep and superficial), erythema perstans, erythema gyratum perstans, erythema gyratum repens, darier erythema (deep gyrate erythema) and erythema figuratum perstans.

Erythema nodosum is a form of panniculitis characterised by tender red nodules, 1–10 cm, associated with systemic symptoms including fever, malaise, and joint pain. Nodules may become bluish-purple, yellowing, and green, and subside over a period of 2–6 weeks without ulcerating or scarring. Erythema nodosum is associated with infections, including Hepatitis C, EBV and tuberculosis, Crohn's disease and sarcoidosis, pregnancy, medications including sulfonamides, and some cancers, including Non-Hodgkin lymphoma and pancreatic cancer.

Discoid lupus erythematosus (DLE) is a chronic skin condition of sores with inflammation and scarring favouring the face, ears, and scalp and at times on other body areas. These lesions develop as a red, inflamed patch with a scaling and crusty appearance. The centre areas may appear lighter in colour with a rim darker than the normal skin.

Discoid lupus erythematosus can be divided into localised, generalised, and childhood discoid lupus erythematosus.

Non-vasculitis forms of panniculitis that may occur include:

- "Cytophagic Histiocytic Panniculitis" was first described in 1980 by Winkelmann as a chronic histiocytic disease of the subcutaneous adipose tissue, which is characterized clinically by tender erythematous nodules, recurrent high fever, malaise, jaundice, organomegaly, serosal effusions, pancytopenia, hepatic dysfunction and Coagulation abnormalities. CHP may occur either isolated or as part of cutaneous manifestations of Hemophagocytic syndrome (HPS). CHP is a rare and often fatal form of panniculitis with multisystem involvement. But it can also present in a benign form involving only the subcutaneous tissue, thus having a broad clinical spectrum.

- "Traumatic panniculitis" is a panniculitis that occurs following trauma to the skin.

- "Cold panniculitis" is a panniculitis occurring after exposure to cold, most often seen in infants and young children. This condition has been described in children who suck ice or popsicles, and therefore is sometimes referred to as "popsicle panniculitis." The term was coined when a patient with a rash of unknown origin on her cheek was taken to a dermatologist.

- "Gouty panniculitis" is a panniculitis caused by deposition of uric acid crystals in gout.

- "Pancreatic panniculitis" (also known as "Enzymatic panniculitis," "Pancreatic fat necrosis," and "Subcutaneous fat necrosis") is a panniculitis most commonly associated with pancreatic carcinoma, and more rarely with anatomic pancreatic abnormalities, pseudocysts, or drug-induced pancreatitis.

- "Factitial panniculitis" is a panniculitis that may be induced by the injection of organic materials, povidone, feces, saliva, vaginal fluid, and oils.

The rash is composed of small papular lesions, each on a separate reddened base.

It can be caused by infection, massage, electrical treatment, acne medication, allergies, exercise, solar radiation (sunburn), cutaneous radiation syndrome, mercury toxicity, blister agents, niacin administration, or waxing and tweezing of the hairs—any of which can cause the capillaries to dilate, resulting in redness. Erythema is a common side effect of radiotherapy treatment due to patient exposure to ionizing radiation.

Fever and a non specific skin eruption – with reddening (erythema) and swelling (oedema) of the skin – are the most common symptoms of NEH. Patients usually present with the skin eruption 1-2 weeks after use of the cytotoxic drug. Sometimes, the skin eruption can be painful. Skin eruptions can be located on the extremities, trunk, and face. Severe lesions are rare, and can mimic cellulitis. Generalised lesions resembling erythema multiforme have been reported.

Erythema multiforme major (also known as "erythema multiforme majus") is a form of rash with skin loss or epidermal detachment.

The term "erythema multiforme majus" is sometimes used to imply a bullous (blistering) presentation.

According to some sources, there are two conditions included on a spectrum of this same disease process:

- Stevens–Johnson syndrome (SJS)

- Toxic epidermal necrolysis (TEN) which described by Alan Lyell and previously called Lyell syndrome[5].

In this view, EM major, SJS and TEN are considered a single condition, distinguished by degree of epidermal detachment.

However, a consensus classification separates erythema multiforme minor, erythema multiforme major, and SJS/TEN as three separate entities.

Palmar erythema is reddening of the palms at the thenar and hypothenar eminences.

Erythema induratum is a panniculitis on the calves. It occurs mainly in women, but it is very rare now. Historically, when it has occurred, it has often been concomitant with cutaneous tuberculosis, and it was formerly thought to be always a reaction to the tuberculum bacillus. It is now considered a panniculitis that is not associated with just a single defined pathogen. The medical eponym Bazin disease was historically synonymous, but it applies only to the tuberculous form and is dated.

Erythema multiforme (EM) is a skin condition of unknown cause; it is a type of erythema possibly mediated by deposition of immune complexes (mostly IgM-bound complexes) in the superficial microvasculature of the skin and oral mucous membrane that usually follows an infection or drug exposure. It is an uncommon disorder, with peak incidence in the second and third decades of life. The disorder has various forms or presentations, which its name reflects ("multiforme", "", from "" + ""). Target lesions are a typical manifestation. Two types, one mild to moderate and one severe, are recognized (erythema multiforme minor and erythema multiforme major).

Erythema toxicum neonatorum (also known as erythema toxicum, urticaria neonatorum and toxic erythema of the newborn) is a common rash in neonates. It appears in up to half of newborns carried to term, usually between day 2–5 after birth; it does not occur outside the neonatal period.

Erythema toxicum is characterized by blotchy red spots on the skin with overlying white or yellow papules or pustules. These lesions may be few or numerous. The eruption typically resolves within first two weeks of life, and frequently individual lesions will appear and disappear within minutes or hours. It is a benign condition thought to cause no discomfort to the baby.

While the presence of lesions is the denominator among patients with PNP, the characteristics of the lesions differ. The five clinical presentations of lesions associated with PNP include:

- "Pemphigus-like": Flaccid blister (discrete), crusts over the raw exuding skin lesions

- "Pemphigoid-like": Tense blister(s) on brick red erythema

- "Erythema multiforme-like": Severe polymorphic skin and/or mucous membrane lesions

- "Graft-vs.-host disease-like": Widespread lichenoid eruption with severe mucous membrane involvement

- "Lichen planus-like": Small red flat-topped scaly papules

It is most common that mucous membrane lesions of the oral cavity are presented first. They can involve the oropharynx, nasopharynx, tongue, and vermilion (red portion) of the lips. They are also known to develop in the conjunctiva of the eye, anogenital (perineum) region, and esophagus. Cutaneous lesions tend to follow the onset of mucosal lesions. The blisters often erupt in waves, usually affecting the upper trunk, head, neck, and proximal extremities. Pemphigoid-like lesions are seen more often on the extremities. Lichenoid lesions are more common among children, presenting on the trunk and limbs, ranging from small red scaly papules to extensive violet to brown papules extending to the face and neck. Within the spectrum of lichenoid presentations are wounds that have features of erythema multiforme and graft-vs.-host disease. Scaly lesions on the palms of the hand and soles of the feet have been noted to coincide with the lichenoid lesions. Lesions of varying morphology may present simultaneously and transform from one type to another as the disease progresses.

Baboon syndrome affects both sexes equally, and can occur at any age, but seems to be more common in childhood than in adulthood.

The areas most affected are the toes, fingers, earlobes, nose.

- Blistering of affected area

- Burning and itching sensation in extremities

- Dermatitis in extremities

- Digital ulceration (severe cases only)

- Erythema (blanchable redness of the skin)

- Pain in affected area

- Skin discoloration, red to dark blue

Chilblains usually heal within 7–14 days.