What Is Cellulitis?

Overview

Cellulitis is a bacterial skin infection that affects the deep layers of the skin, including the subcutaneous tissues and the dermis. Streptococcus and Staphylococcus bacteria species typically cause cellulitis. This bacterial infection can affect anywhere in your body but is mainly found legs, feet, arms, and face. This is commonly present with redness, warmth, swelling, and pain in the affected area. Everyone can get episodes of cellulitis, but people with diabetes and weakened immune systems are more prone to get cellulitis. This can be and should be diagnosed promptly and treated with antibiotics. However, untreated cellulitis will cost you your limb or your life. In this article, we will discuss the causes, symptoms, management, treatment options, and FAQs about cellulitis.

Causes of cellulitis

Our skin acts as a protective barrier by preventing microorganisms like bacteria which are commonly found on the skin's surface, from reaching the deep layers of the skin.¹ However, when there is a breach or crack on the skin surface these bacteria enter deep layers of the skin and cause infection. Skin break can occur due to several reasons.

• Trauma due to insect bites, scratches, or burns
• Chronic leg wounds
• Fungal infection between the toes (tinea pedis)
• Skin conditions like eczema/ psoriasis
• Surgical wounds

Most of the time you cannot identify a skin breach visible to the naked eye. Cellulitis is not contagious so you cannot catch cellulitis from someone else.

There are some conditions that increase the risk of developing cellulitis. These conditions either increase the risk of skin being damaged or weaken your body's strength to fight infections by weakening your immune system. A few of these conditions are mentioned below.^2,3,4

• Lymphoedema which accumulates fluid under your skin
• Leg swelling as a result of poor mobility
• Venous insufficiency and history of venous surgery
• Obesity which causes poor circulation in your legs and arms
• Pregnancy which stretches your skin and causes leg swelling
• A weakened immune system due to causes like HIV and AIDS, diabetes, or chemotherapy treatment
• Frequent drug injections that damage your skin and increase the chance of bacteria being administered into your body
• A previous episode of cellulitis

There are a few bacterial species that cause cellulitis. The most common causative bacteria are:

• Streptococcus pyogenes
• Staphylococcus aureus

Signs and symptoms of cellulitis

If left untreated, cellulitis can lead to serious complications, such as sepsis or even death. Therefore, it is important to recognize the signs and symptoms of cellulitis and seek medical attention promptly.⁵

• Redness of the affected skin
  • The area of redness may be small at first, but it can spread to adjacent areas if untreated
• Swelling of the affected area
  • The affected area of the skin may look swollen without clear margins
• Warmth
  • The skin may feel warm to the touch because of the infection going on inside
• Shiny skin
  • Because of the swelling and stretching of the skin, it may become shiny
• Pain during palpation
  • The affected area may feel sensitive and sore and it may hurt to touch
• Lymph node swelling
  • Lymph nodes are part of the body's immune system and are responsible for filtering out and fighting harmful substances. When the body is fighting an infection, the lymph nodes may become swollen and tender. If cellulitis is present, the lymph nodes near the affected area may enlarge and become tender
• Skin blistering
  • This can be seen in more advanced cases. Fluid-filled small blisters may present on the skin, which makes it more viable to further infections when they break open

In addition to the above local signs and symptoms, you can have more generalized symptoms associated with the above local symptoms. These symptoms usually present when the infection has spread beyond the skin.¹

• Fever
  • This may indicate that the infection is spreading beyond the affected area. A body temperature of 100.4°F (38°C) or higher is defined as fever
• Chills
  • A feeling of coldness associated with shivering can be seen in a more generalized infection
• Headache
• Fatigue and malaise

Generally, cellulitis affects limbs but sometimes it can cause periorbital cellulitis (Preseptal cellulitis) which is swelling and infection of the eyelid and surroundings without involving the eyeball (Orbit).⁶ In periorbital cellulitis you may experience symptoms such as:

• Redness around the eye
• Swelling around the eye
• Redness of sclera (white part of the eye)
• Pain around the eye

In some rare cases, periorbital cellulitis can progress into orbital cellulitis, which is considered a surgical emergency and can cause loss of vision if not treated promptly.

Conditions that mimic cellulitis

Cellulitis is a common infection of the dermis and subcutaneous tissue of the skin, mainly affecting the legs and arms. There are conditions that mimic cellulitis.

• Necrotising fasciitis or flesh-eating disease
  • Necrotising fasciitis is a more serious bacterial infection that leads to the destruction and decay (necrosis) of subcutaneous tissues. This condition shares symptoms of cellulitis on a higher scale. Necrotising fasciitis usually causes severe pain which is disproportionate to the size of the wound. Unlike cellulitis, necrotising fasciitis progresses rapidly and it qualifies as an emergency that needs inpatient treatment and surgical interventions
• Erysipelas¹
  • This is the other similar condition that mimics cellulitis. Erysipelas is considered a form of cellulitis that affects the superficial layers of the skin. However, unlike in cellulitis, the affected area is well-demarcated and mildly reddened in erysipelas. This is also a bacterial infection and is treated with antibiotics

Diagnosis of cellulitis

Your healthcare provider will diagnose cellulitis clinically, by the condition of the affected skin area and the presence of generalized symptoms. Blood investigations (blood culture) will be performed if there are signs of sepsis.

Management and treatment for cellulitis

Treatment and management of cellulitis will include treating the acute infection along with the management of symptoms and other underlying diseases (e.g. Diabetes).¹

Antibiotics are the mainstay of treatment while other supportive treatments are given to alleviate symptoms.¹ The mode of administration of antibiotics depends on the severity of the condition and the presence of other risk factors.

For mild cellulitis involving only a small area of the skin, your doctor will prescribe oral antibiotics (drugs taken by mouth). Usually, you should feel better after 48 hours of the commencement of the treatment. You should contact your GP if you do not feel better even after 48 hours. The most important thing is to continue taking antibiotics until the full course is over, even if you feel better after a few doses.

For severe cellulitis, you will be treated with intravenous antibiotics (injections) as an inpatient. The choice of antibiotics changes from the usual antibiotics if methicillin-resistant staphylococcus aureus (MRSA) infection is suspected.¹ 

You will be hospitalised and managed if you belong to one of the below groups.

• Have a generalized infection
• Have failed outpatient treatment
• Have a weakened immune system
• Inability to tolerate oral medications

To improve healing and relieve other symptoms, you can take supportive measures. Some of these measures are also important in the prevention of recurrent cellulitis.⁷

• You can take Paracetamol to relieve pain
• If the affected area is on your arm or leg, elevating the affected area may improve the swelling as well as will reduce the pain
• Mobilizing the joints near the affected area will prevent them from getting stiff
• Drinking plenty of fluids to avoid dehydration
• Keeping skin moisturized and clean
• Keeping the wounds clean
• Wearing footwear and appropriate clothing when working outdoors
• Maintaining good foot hygiene to avoid getting fungal infections

FAQs

How is cellulitis diagnosed

Your doctor will diagnose cellulitis clinically. However, if you show signs of sepsis a blood culture will be performed.

How can I prevent cellulitis

Cellulitis is a bacterial infection of the deep layers of the skin. When there is a skin breach normal skin flora reach the deep layers and cause the infection. Therefore, to prevent cellulitis you can take good care of your skin by:

• Drinking plenty of water to keep the skin moisturized, to prevent cracking
• Keeping the skin clean
• Maintaining good foot hygiene
• Taking regular treatments for underlying conditions like diabetes to keep them optimally controlled
• Wearing appropriate footwear and gloves when working outside
• Eating a healthy diet and regular exercises to keep the body weight in the healthy range

Who are at risks of cellulitis

You have a higher risk of getting cellulitis if you have:

• Lymphoedema which accumulates fluid under your skin
• Leg swelling as a result of poor mobility
• Venous insufficiency and history of venous surgery
• Obesity which causes poor circulation in your legs and arms
• Pregnancy which stretches your skin and causes leg swelling
• A weakened immune system due to causes like HIV/AIDS, diabetes, or chemotherapy treatment
• Frequent drug injections that damage your skin and increase the chance of bacteria being administered into your body
• A previous episode of cellulitis

How common is cellulitis

Cellulitis affects 1 in 40 people per year in the UK.⁷

When should I see a doctor

Cellulitis can be treated completely by prompt treatments. You should see your doctor immediately if you notice: 

• Redness
• Swelling
• Warmth

on your skin as these are initial symptoms of cellulitis.

You need to contact emergency services or should immediately visit A&E if your symptoms progressed into the below as they indicate a more serious life-threatening infection.

• High temperature (body temperature of 100.4°F (38°C) or higher)
• Rapid heartbeat or rapid breathing
• Affected skin turned purple or blackish
• Dizziness and faintishness
• Disorientation
• Loss of consciousness

Summary

Cellulitis is a bacterial skin infection that can be resolved by treating promptly with antibiotics. People who have weakened immune systems due to diabetes-like conditions, people who are obese, and taking frequent drug injections are at high risk of getting cellulitis. The main causative organisms are Streptococcus and Staphylococcus bacterial species.

Initial symptoms of cellulitis are redness, swelling, and warmth around the infected area. In more severe infections blisters and more generalized symptoms like fever, faintishness, and headache will be experienced. The majority of the cases can be treated with oral antibiotics while severe infections require inpatient treatment with intravenous antibiotics.

The take-home message is cellulitis is easily treatable if you immediately seek medical advice. However, untreated cellulitis can be life-threatening and can even cause death.