Cellulitis
Introduction
What is cellulitis?
Cellulitis is an infection of the deeper layers of skin and the underlying tissue. The main symptom of cellulitis is the affected area of skin suddenly turning red, swollen, painful and hot.
Cellulitis can have a wide range of causes, although it is usually caused by a type of bacteria called group A streptococcus.
The skin
The skin is the largest organ of the human body. It is made up of three main layers:
- the epidermis – the outer surface of skin and an underlying section of cells, which the body uses to create new skin cells
- dermis – the middle layer of skin that contains blood vessels, sweat glands and hair follicles (holes in the skin where hair grows out)
- subcutis – the bottom layer of skin that consists of a layer of fat and collagen (a tough, spongy protein), which helps protect the body and regulate temperature
Cellulitis develops when the normally harmless bacteria (or sometimes fungi) move down through the skin's surface and into the dermis and subcutis through a damaged or broken area of skin, such as a cut, burn or bite.
Having a skin condition, such as eczema, or a fungal infection of the foot or toenails (athlete’s foot) can cause small breaks and cracks to develop in the sufrace of the skin. This makes a person vulnerable to cellulitis.
How common is cellulitis?
Cellulitis is a fairly uncommon condition but it is certainly not rare.
Cellulitis can affect people of all ages, including children. Rates are thought to be roughly similar in both sexes.
Annual cases of cellulitis has increased three-fold over the past 15 years. It is unclear whether this is due to certain strains of bacteria becoming more virulent (more likely to cause an infection) or the risk factors for cellulitis becoming more widespread. It is possible that the rise in the number of cases may be due to a combination of both factors.
Known risk factors for cellulitis include:
- having a weakened immune system (the body’s natural defence against infection and illness) as a result of health conditions such as HIV or diabetes, or as a side effect of a treatment such as chemotherapy
- lymphoedema – a condition that causes swelling of the arms and legs, which can sometimes occur spontaneously or may develop after surgery for some types of cancer
- intravenous drug misuse (injecting drugs such as heroin)
Outlook
The outlook for cellulitis is good if it is diagnosed and treated promptly. The condition usually responds well to treatment with antibiotics. As a precaution, hospital admission is usually recommended for more severe cases of cellulitis that fail to respond to antibiotic tablets.
Complications of cellulitis usually involve the bacteria triggering a secondary infection somewhere else in the body, such as in the blood (septicaemia). Such cases usually require hospital admission for treatment with intravenous antibiotics (antibiotics given directly into a vein).
Most deaths occur in elderly people who were already seriously ill with another condition.
Cellulitis vs cellulite
Cellulite is a cosmetic problem that is caused by fatty deposits that form under the skin, and it has no relation to cellulitis.
Losing weight is the best way of dealing with cellulite. See the Lifestyle and Well-being section of the website for information and advice.
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Symptoms
Cellulitis most commonly affects one of your legs, but symptoms can develop in any area of your body. The condition affects your skin in several ways, causing it to become:
- red
- painful
- hot
- swollen
- tender
If you have cellulitis, you may also find that blisters develop on your skin.
Cellulitis can make you feel generally unwell, that develop before, or in combination with, changes to your skin, causing symptoms such as:
- nausea
- shivering
- chills
- a general sense of feeling unwell
When to seek urgent medical advice
There are a number of symptoms that suggest the infection has begun to spread from your skin to other parts of your body, such as your blood. These symptoms include:
- the affected area of skin changes appearance and may begin to spread rapidly
- high temperature (fever) of 38ºC (100.4ºF) or above
- vomiting
- changes in mental state, such as confusion
- rapid heart beat
- rapid breathing
- dizziness, particularly when moving from a lying or sitting position to a standing one
If you have any of these symptoms, go to your nearest accident and emergency (A&E) department as soon as possible because you may need urgent medical attention.
It is also recommended that you visit A&E if you suspect that you have cellulitis and you have a pre-existing condition that makes you more vulnerable to complications arising from infection, such as having a weakened immune system.
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Causes
Most cases of cellulitis are caused by a bacterial infection of the skin and the tissues underneath the skin.
See the Health topic about Streptococcal infections for more information.
Cellulitis usually occurs when the surface of your skin becomes damaged. It creates an entry point for the bacteria, allowing it to attack the skin and tissue underneath. A break in the skin may be caused by a:
The break in the skin may be so small that it cannot be easily identified.
Some cases of cellulitis can develop if a wound or other break in the skin is exposed to water that is contaminated with bacteria.
A fungal infection is a much rarer cause of cellulitis. Fungal cellulitis usually only affects people with a severely weakened immune system, such as a person in the final stages of an HIV infection that is not responding to treatment.
Risk factors
There are a number of factors and other conditions which may increase your risk of developing cellulitis. These include:
- being obese (excessively overweight)
- having a weakened immune system
- having poorly controlled diabetes
- having circulation problems
- having chickenpox and shingles
- having lymphoedema
- intravenous drug use
- having previous episodes of cellulitis
These factors are briefly discussed below.
Obesity
Being obese can cause swelling in your legs, which may increase your risk of developing cellulitis. Obesity is defined as being very overweight with a body mass index (BMI) of 30 or more. To check your BMI, you can use the healthy weight calculator.
A weakened immune system
Your immune system may be weakened if you are undergoing chemotherapy, or you have a condition such as HIV or AIDS. If your immune system is weakened, it makes it harder for your body to fight off infection.
A number of treatments are also known to weaken the immune system. For example:
- chemotherapy – a cancer treatment that uses medication to kill cancerous cells
- immunosuppressants (medications that are widely used to treat people who have had organ transplants to prevent their body rejecting the donated organ)
- long-term use of corticosteroids tablets and corticosteroid creams
Poorly controlled diabetes
If you have diabetes (type 1 or type 2) that is not adequately treated or controlled, it can weaken your immune system. Poorly controlled diabetes can also affect your circulation, which can sometimes cause skin ulcers to develop. Skin ulcers are a common entry point for bacteria.
Circulation problems
Poor circulation can increase your risk of developing skin infections in the places where your body does not have adequate blood supply. For example, many people with diabetes have a reduced blood supply to their feet, which makes them more vulnerable to developing cellulitis.
Chickenpox and shingles
Chickenpox and shingles often cause blisters to develop on your skin. Chickenpox (which usually only affects children) and shingles (which usually affects people aged 50 and older) are viral infections caused by the herpes varicella-zoster virus.
If the blisters are broken or scratched, it can damage your skin and provide an entry point for bacteria.
Lymphoedema
Lymphoedema is a condition that causes fluid to build up under your skin. It may occur following surgery for some cancers. If your skin becomes very swollen it may crack, creating an entry point for bacteria.
Intravenous drug use
People who inject illegal drugs have an increased risk of developing cellulitis because poor needle hygiene, such as not sterilising the needle before and after injections, can increase the risk of infection.
Previous episodes of cellulitis
If you have had a previous episode of cellulitis, your risk of having further episodes in the future will be increased.
An estimated 20-30% of people with a previous history of cellulitis will be admitted to hospital again with another cellulitis infection. The average time between a previous and recurring cellulitis infection is three years.
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Diagnosis
Your GP will normally be able to diagnose cellulitis by assessing your symptoms and examining your skin.
Before making a diagnosis, your GP may want to rule out other conditions which may cause your skin to become red and inflamed, such as varicose eczema (an itchy skin condition that causes inflammation and, sometimes, skin ulcers).
If you have an open wound in your skin, your GP may take a swab of cells from the wound to see what type of bacteria is causing the infection. A swab looks similar to a cotton bud and it is used to remove small traces of tissue for testing.
Further testing may be carried out if your symptoms are serious enough to warrant admission to hospital. Testing usually involves a series of blood tests, which are an effective way of assessing the severity of the infection and how well you are responding to the antibiotics. See Cellulitis - treatment for more information.
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Treatment
Your treatment plan
If you are diagnosed with cellulitis, your recommended treatment plan will depend on your general state of health and the severity of your symptoms.
You can usually be treated at home with antibiotic tablets if:
- you do not have any symptoms (such as nausea and vomiting) that would suggest the cellulitis infection has spread from your skin to other parts of the body
- there are no other factors that make you more vulnerable to infection, such as having a weakened immune system or poor circulation
If this is not the case, admission to hospital is usually recommended, and you will be injected with antibiotics.
Treatment at home
Antibiotics
If it is thought that you are well enough to be treated at home, you will be given a seven-day course of antibiotic tablets.
The most commonly prescribed antibiotic medicine for cellulitis is flucloxacillin, which is part of the penicillin group of antibiotics.
The most common side effects of flucloxacillin are mild digestive problems, such as an upset stomach or episodes of diarrhoea.
If you cannot take flucloxacillin because you are allergic to penicillin, an alternative antibiotic may be prescribed called erythromycin.
The side effects of erythromycin are usually mild and short-lived. They include:
- nausea
- abdominal (tummy) discomfort
- vomiting
- diarrhoea
If it is suspected that your cellulitis was caused by a wound in your skin being exposed to contaminated water you may either be prescribed a combination of two different antibiotics: doxycycline or ciprofloxacin in combination with flucloxacillin or erythromycin.
You may notice that your skin initially becomes redder when you first start taking the antibiotics, but this is normally only a temporary reaction. The redness should start to fade within 48 hours.
If your symptoms get worse 48 hours after you start taking the antibiotics, or you start to develop symptoms such as a high temperature, or vomiting, you should contact your GP immediately.
Self-care
If you have cellulitis, there are some things that you can do at home in order to help ease your symptoms and speed your recovery.
You should drink plenty of water to help prevent you becoming dehydrated. If your leg is affected by cellulitis, you should keep it raised because this should make you feel more comfortable, and help to reduce the swelling.
Pain relief
If your cellulitis is causing pain or a high temperature (fever), an over-the-counter painkilling medication may ease your symptoms. Paracetamol and ibuprofen are suitable for cellulitis.
Hospital treatment
If you need to be admitted for hospital treatment, you will be given antibiotics intravenously (through a vein in your arm).
The type of antibiotics that will be used depends on the suspected cause of your infection, although a type of antibiotic known as a broad-spectrum antibiotic is often used. This type of antibiotic can kill a range of different strains of bacteria.
If your symptoms improve and you are otherwise healthy, you may be discharged after 48 hours and your treatment can switch to antibiotic tablets.
If this is not the case, a three- to four-day course of intravenous antibiotics is usually recommended before switching over to antibiotic tablets.
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Complications
Blood poisoning
If the bacteria which infects your skin and tissue gets into your bloodstream, it can cause blood poisoning (septicaemia). Symptoms of blood poisoning (septicaemia) may include:
- high temperature (fever) of 38ºC (100.4ºF) or above
- fast heart beat
- fast breathing
- low blood pressure (hypotension), which will cause you to feel dizzy when you stand up
- a change in mental behaviour, such as confusion or disorientation
- diarrhoea
- reduced urine flow
- cold, clammy skin
- pale skin
- loss of consciousness
If you have any of these symptoms call 999 for an ambulance.
See the Health topic about Blood poisoning for more information about this condition.
Abscess
Some cases of cellulitis can result in an abscess forming near the site of the infection. An abscess is a swollen, pus-filled lump under the surface of the skin. It is caused by a build-up of bacteria and dead white blood cells.
In some cases, the antibiotics that are used to treat cellulitis may also help to remove the abscess. However, if this is not the case, the pus will have to be drained from the abscess through a small cut in your skin.
See the Health topic about Abscess for more information.
Facial cellulitis and meningitis
Facial cellulitis is an uncommon form of cellulitis that develops on the skin of the face. It accounts for an estimated 8.5% of all cases of cellulitis.
Facial cellulitis is most common in children under three years old and older adults above 50. If facial cellulitis is left untreated in children, the bacteria can potentially spread to the outer membranes of their brain (the meninges) and trigger a serious brain infection called meningitis.
Symptoms of meningitis can differ in adults, but symptoms in babies and children under three years old include:
- becoming floppy and unresponsive, or stiff with jerky movements
- becoming irritable and not wanting to be held
- unusual crying
- vomiting and refusing feeds
- pale and blotchy skin
- loss of appetite
- staring expression
- very sleepy and reluctant to wake up
Bacterial meningitis is very serious and should be treated as a medical emergency. If left untreated, a bacterial infection can cause severe brain damage and infect the blood.
If you suspect that your child has symptoms of meningitis, call 999 immediately for an ambulance.
The best way to protect your child against meningitis is to make sure they have been vaccinated with the:
- DTaP/IPV/Hib (5-in-1) vaccination, which should be given between the ages of two and four months
- the Hib/MenC booster, which should be given after the child’s first birthday
The vaccine and the booster provide immunity against two leading causes of meningitis in children:
- haemophilus influenzae type b bacteria
- group C meningococcal bacteria
Ask your GP if you are unsure whether your child’s vaccinations are up to date.
See the Health topic about Meningitis and Immunisations, childhood and Immunisations, adult for more information.
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Prevention
Not all cases of cellulitis can be prevented. However, there are steps that you can take to reduce the risk of developing the condition, as well as other forms of infections.
Treating skin wounds
Make sure that any cuts, grazes or bites are kept clean. Wash the damaged skin under running tap water and, if necessary, apply an antiseptic cream.
Keep the wound covered with a plaster or dressing. Make sure that you change the plaster or dressing, if it becomes wet or dirty. Plasters and dressings will reduce the risk of the wound being damaged further, and they will help to create a barrier against bacteria entering the skin.
Keep your fingernails short
If you have an itchy skin condition, such as atopic eczema or chickenpox, keep your fingernails clean and short at all times.
If you scratch your skin and your fingernails are short and clean, the risk of skin damage and infection will be reduced. Wash your hands regularly, particularly when treating or touching your wound or skin condition.
Keep your skin moisturised
If your skin is dry or prone to cracking, keep your skin well moisturised. Cracked skin can create an entry point for bacteria.
Preventing cellulitis in lymphoedema
People with lymphoedema (a condition that causes swelling of the arms and legs) have a much higher risk of developing cellulitis than the population at large. This is because the swelling of the skin that is associated with lymphoedema makes it more vulnerable to bacterial infection.
If you are diagnosed with lymphoedema, you may be given a two-week course of antibiotics to take in case you start having the initial symptoms of cellulitis.
If you have two or more episodes of cellulitis in a year, it is usually recommended that you begin taking antibiotics on a long-term basis to protect against further infection.
See the Health topic about Lymphoedema for more information about the condition.
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