The first symptom is a sudden onset of swelling of the face, which develops within two days into papules and pustues on the lips, nose, and around the eyes. These pustules release a purulent discharge, causing a crust to form on the skin. There is also lymphadenopathy (swelling of lymph nodes) in the main lymph nodes of the head. The feet, body, prepuce or perianal area may be affected. Pustular otitis externa can occur, with the pinnae (ear flaps) becoming thickened by edema. Affected areas are painful but not itchy. Approximately half of affected puppies have lethargy and depression. Less common symptoms include pyrexia, anorexia, and joint pain, caused by sterile suppurative arthritis.

Juvenile cellulitis, also known as puppy strangles or juvenile pyoderma, is an uncommon disease of dogs. Symptoms include dermatitis, lethargy, depression and lameness. When puppies are first presented with what appears to be staphylococcal pyoderma, juvenile cellulitis, a relatively rare condition, may not be considered.

The typical signs and symptoms of cellulitis is an area which is red, hot, and painful. The photos shown here of are of mild to moderate cases, and are not representative of earlier stages of the condition.

Cellulitis is caused by a type of bacteria entering the skin, usually by way of a cut, abrasion, or break in the skin. This break does not need to be visible. Group A "Streptococcus" and "Staphylococcus" are the most common of these bacteria, which are part of the normal flora of the skin, but normally cause no actual infection while on the skin's outer surface.

About 80% of cases of Ludwig's angina, or cellulitis of the submandibular space, are caused by dental infections. Mixed infections, due to both aerobes and anaerobes, are commonly associated with this type of cellulitis. Typically, this includes alpha-hemolytic streptococci, staphylococci, and bacteroides groups.

Predisposing conditions for cellulitis include insect or spider bite, blistering, animal bite, tattoos, pruritic (itchy) skin rash, recent surgery, athlete's foot, dry skin, eczema, injecting drugs (especially subcutaneous or intramuscular injection or where an attempted intravenous injection "misses" or blows the vein), pregnancy, diabetes, and obesity, which can affect circulation, as well as burns and boils, though debate exists as to whether minor foot lesions contribute. Occurrences of cellulitis may also be associated with the rare condition hidradenitis suppurativa or dissecting cellulitis.

The appearance of the skin assists a doctor in determining a diagnosis. A doctor may also suggest blood tests, a wound culture, or other tests to help rule out a blood clot deep in the veins of the legs. Cellulitis in the lower leg is characterized by signs and symptoms similar to those of a deep vein thrombosis, such as warmth, pain, and swelling (inflammation).

This reddened skin or rash may signal a deeper, more serious infection of the inner layers of skin. Once below the skin, the bacteria can spread rapidly, entering the lymph nodes and the bloodstream and spreading throughout the body. This can result in influenza-like symptoms with a high temperature and sweating or feeling very cold with shaking, as the sufferer cannot get warm.

In rare cases, the infection can spread to the deep layer of tissue called the fascial lining. Necrotizing fasciitis, also called by the media "flesh-eating bacteria", is an example of a deep-layer infection. It is a medical emergency.

This most common form of impetigo, also called nonbullous impetigo, most often begins as a red sore near the nose or mouth which soon breaks, leaking pus or fluid, and forms a honey-colored scab, followed by a red mark which heals without leaving a scar. Sores are not painful, but they may be itchy. Lymph nodes in the affected area may be swollen, but fever is rare. Touching or scratching the sores may easily spread the infection to other parts of the body.

Skin ulcers with redness and scarring also may result from scratching or abrading the skin.

Tuberculous cellulitis is a skin condition resulting from infection with mycobacterium, and presenting as cellulitis.

Ecthyma, the nonbullous form of impetigo, produces painful fluid- or pus-filled sores with redness of skin, usually on the arms and legs, become ulcers that penetrate deeper into the dermis. After they break open, they form hard, thick, gray-yellow scabs, which sometimes leave scars. Ecthyma may be accompanied by swollen lymph nodes in the affected area.

Boils are bumpy, red, pus-filled lumps around a hair follicle that are tender, warm, and very painful. They range from pea-sized to golf ball-sized. A yellow or white point at the center of the lump can be seen when the boil is ready to drain or discharge pus. In a severe infection, an individual may experience fever, swollen lymph nodes, and fatigue. A recurring boil is called chronic furunculosis. Skin infections tend to be recurrent in many patients and often spread to other family members. Systemic factors that lower resistance commonly are detectable, including: diabetes, obesity, and hematologic disorders. Boils can be caused by other skin conditions that cause the person to scratch and damage the skin.

Boils may appear on the buttocks or near the anus, the back, the neck, the stomach, the chest, the arms or legs, or even in the ear canal. Boils may also appear around the eye, where they are called styes. A boil on the gum is called intraoral dental sinus, or more commonly, a gumboil.

Cutaneous group B streptococcal infection may result in orbital cellulitis or facial erysipelas in neonates.

Common signs and symptoms of orbital cellulitis include pain with eye movement, sudden vision loss, chemosis, bulging of the infected eye, and limited eye movement. Along with these symptoms, patients typically have redness and swelling of the eyelid, pain, discharge, inability to open the eye, occasional fever and lethargy. It is usually caused by a previous sinusitis. Other causes include infection of nearby structures, trauma and previous surgery.

Eosinophilic cellulitis, also known as Wells' syndrome, is a skin disease that presents with painful, red, raised, and warm patches of skin. The rash comes on suddenly, lasts for a few weeks, and often repeatedly comes back. Scar formation does not typically occur.

Eosinophilic cellulitis is of unknown cause. It is suspected to be an autoimmune disorder. It may be triggered by bites from insects such as spiders, fleas, or ticks, or from medications or surgery. Diagnosis is made after other potential cases are ruled out. Skin biopsy of the affected areas may show an increased number of eosinophils. Other conditions that may appear similar include cellulitis, contact dermatitis, and severe allergic reactions such as anaphylaxis.

Treatment is often with a corticosteroids. Steroids applied as a cream is generally recommended over the use of steroids by mouth. Antihistamines may be used to help with itchiness. Many times the condition goes away after a few weeks without treatment. The condition is uncommon with about 200 described cases. It affects both sexes with the same frequency. It was first described by George Crichton Wells in 1971.

Complications include hearing loss, blood infection, meningitis, cavernous sinus thrombosis, and optic nerve damage (which could lead to blindness).

Aeromonas infections may cause skin infections manifesting as cellulitis, pustules, and furuncles. An infection usually only causes mild infections of the skin but can also cause a more a serious infection called gastroenteritis?

Periorbital cellulitis must be differentiated from orbital cellulitis, which is an emergency and requires intravenous (IV) antibiotics. In contrast to orbital cellulitis, patients with periorbital cellulitis do not have bulging of the eye (proptosis), limited eye movement (ophthalmoplegia), pain on eye movement, or loss of vision. If any of these features is present, one must assume that the patient has orbital cellulitis and begin treatment with IV antibiotics. CT scan may be done to delineate the extension of the infection.

Affected individuals may experience the following;

swelling,

redness,

discharge,

pain,

shut eye,

conjunctival injection,

fever (mild), slightly blurred vision, teary eyes, and some reduction in vision.

Typical signs include periorbital erythema, induration, tenderness and warmth.

A boil, also called a furuncle, is a deep folliculitis, infection of the hair follicle. It is most commonly caused by infection by the bacterium "Staphylococcus aureus", resulting in a painful swollen area on the skin caused by an accumulation of pus and dead tissue. Boils which are expanded are basically pus-filled nodules. Individual boils clustered together are called carbuncles.

Most human infections are caused by coagulase-positive "S. aureus" strains, notable for the bacteria's ability to produce coagulase, an enzyme that can clot blood. Almost any organ system can be infected by "S. aureus".

Dissecting cellulitis of the scalp, also known as dissecting scalp cellulitis, dissecting folliculitis of the scalp, perifolliculitis capitis abscedens et suffodiens of Hoffman, perifolliculitis abscedens et suffodiens, or folliculitis abscedens et suffodiens, is an inflammatory condition of the scalp that can lead to scarring alopecia, which begins with deep inflammatory nodules, primarily over occiput, that progresses to coalescing regions of boggy scalp. Boggy tissue has a high fluid level that results in a spongy feeling.

Isotretinoin proves to be the medicine of choice for the treatment of the disease.

Cutaneous "Streptococcus iniae" infections cause a cellulitis of the hands, usually after a person handles tilapia, as this bacterium is a fish pathogen.

Eosinophilic cellulitis is of unknown cause. It is suspected to be an autoimmune disorder. It may be triggered by bites from insects such as spiders, fleas, or ticks, or from medications or surgery.

Bacterial skin infections include:

- Folliculitis is an infection of the hair follicle that can resemble pimples.

- Impetigo is a highly contagious bacterial skin infection most common among pre-school children. It is primarily caused by "Staphylococcus aureus", and sometimes by "Streptococcus pyogenes".

- Erysipelas is an acute streptococcus bacterial infection of the deep epidermis with lymphatic spread.

- Cellulitis is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin. Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken: cracks in the skin, cuts, blisters, burns, insect bites, surgical wounds, intravenous drug injection or sites of intravenous catheter insertion. Skin on the face or lower legs is most commonly affected by this infection, though cellulitis can occur on any part of the body.

Tufted folliculitis presents with doll's hair-like bundling of follicular units, and is seen in a wide range of scarring conditions including chronic staphylococcal infection, chronic lupus erythematosus, lichen planopilaris, Graham-Little syndrome, folliculitis decalvans, acne keloidalis nuchae, immunobullous disorders, and dissecting cellulitis.

Infection of the skin is distinguished from dermatitis, which is inflammation of the skin, but a skin infection can result in skin inflammation. Skin inflammation due to skin infection is called "infective dermatitis."

Bacterial skin infections affected about 155 million people and cellulitis occurred in about 600 million people in 2013.

A skin and skin structure infection (SSSI), also referred to as skin and soft tissue infection (SSTI) or acute bacterial skin and skin structure infection (ABSSSI), is an infection of skin and associated soft tissues (such as loose connective tissue and mucous membranes). The pathogen involved is usually a bacterial species. Such infections often requires treatment by antibiotics.

Until 2008, two types were recognized, complicated skin and skin structure infection (cSSSI) and uncomplicated skin and skin structure infection (uSSSI). "Uncomplicated" SSSIs included simple abscesses, impetiginous lesions, furuncles, and cellulitis. "Complicated" SSSIs included infections either involving deeper soft tissue or requiring significant surgical intervention, such as infected ulcers, burns, and major abscesses or a significant underlying disease state that complicates the response to treatment. Superficial infections or abscesses in an anatomical site, such as the rectal area, where the risk of anaerobic or gram-negative pathogen involvement is higher, should be considered complicated infections. The two categories had different regulatory approval requirements. The uncomplicated category (uSSSI) is normally only caused by "Staphylococcus aureus" and "Streptococcus pyogenes", whereas the complicated category (cSSSI) might also be caused by a number of other pathogens. In cSSSI, the pathogen is known in only about 40% of cases.

Because cSSSIs are usually serious infections, physicians do not have the time for a culture to identify the pathogen, so most cases are treated empirically, by choosing an antibiotic agent based on symptoms and seeing if it works. For less severe infections, microbiologic evaluation via tissue culture has been demonstrated to have high utility in guiding management decisions. To achieve efficacy, physicians use broad-spectrum antibiotics. This practice contributes in part to the growing incidence of antibiotic resistance, a trend exacerbated by the widespread use of antibiotics in medicine in general. The increased prevalence of antibiotic resistance is most evident in methicillin-resistant "Staphylococcus aureus" (MRSA). This species is commonly involved in cSSSIs, worsening their prognosis, and limiting the treatments available to physicians. Drug development in infectious disease seeks to produce new agents that can treat MRSA.

Since 2008, the U.S. Food and Drug Administration has changed the terminology to "acute bacterial skin and skin structure infections" (ABSSSI). The Infectious Diseases Society of America (IDSA) has retained the term "skin and soft tissue infection".

Chronic inflammation can cause long term lymphatic obstruction. Typically, patients have disorders that present local nodes, primary lymphedema and chronic venous insufficiency. Erysipelas and trauma are major risk factors. Lymphatic edema can be developed in many acral cases accompanied by a thickening of the folds of the skin, hyperkeratosis and papillomatosis. Chronic venous edema is only partially reversible and soon becomes hard, especially confirming tenderness. All structures of the skin are affected. Dilated dermal lymphatic vessels with consequent superior organization and fibrosis result in papillomatosis. As dermal lymphatic stasis progreses, these skin changes become more marked and known as elephantiasis. Occasionally, tissue fibrosis and thickening may become so marked in the later stages of lymphedema that pitting is absent. Recurrent cellulitis, erysipelas and dermato-LAM-adenitis are complications of chronic lymphedema.

Ludwig's angina is a fascial space infection with bilateral involvement of the submandibular, sublingual and submental spaces. The external signs may include bilateral lower facial edema around the mandible and upper neck. Intraoral signs may include a raised floor of mouth due to sublingual space involvement and posterior displacement of the tongue. Symptoms may include dysphagia, pain with swallowing, difficulty breathing, and pain.

Ludwig's angina should be treated urgently due to the airway being compromised. The infection may rapidly spread to other fascial spaces of the head and neck, further compromising the airway.

"Staphylococcus aureus", "Streptococcus pneumoniae", other streptococci, and anaerobes are the most common causes, depending on the origin of the infection.

The advent of the "Haemophilus influenzae" vaccine has dramatically decreased the incidence.