Cellulitis

Cellulitis is an infection of the deeper layers of the skin and the underlying tissue. The main symptom of cellulitis is the affected area of skin suddenly turning red, painful swollen 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 surface 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.

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).

In 2008, there were 25 deaths as a result of cellulitis in Ireland. Most deaths occurred in elderly people who were already seriously ill with another condition.

Antibiotics
Antibiotics are medicines that can be used to treat infections caused by microorganisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
Inflammation
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Cellulitis vs cellulite

Cellulite is a cosmetic problem caused by fatty deposits that form underneath the skin. It is not related to cellulitis.

Losing weight is the best way of dealing with cellulite.

Cellulitis most commonly affects one of your legs, although 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, causing symptoms that develop before, or in combination with, changes to your skin. These symptoms include:

  • nausea
  • shivering
  • chills
  • a general sense of feeling unwell

When to seek medical advice

See your GP as soon as possible if an area of your skin suddenly turns red, painful and hot. If it is not possible for you to see your GP on the same day that your symptoms develop, you should visit your local Emergency Department.

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.

Fever
A high temperature, also known as a fever, is when someone's body temperature goes above the normal 37°C (98.6°F).

Most cases of cellulitis are caused by a bacterial skin infection that affects the tissues beneath the skin.

Cellulitis usually occurs when the surface of your skin is damaged. It creates an entry point for the bacteria, allowing them to attack the skin and tissue underneath. A break in the skin may be caused by a:

  • cut
  • graze
  • burn
  • animal, human or insect bite
  • puncture wound
  • skin ulcer
  • skin condition, such as atopic eczema (this causes the skin to become dry, red and cracked) or athlete's foot

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

A number of factors and other health conditions 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.  

Weakened immune system 

Your immune system may be weakened if you have a condition such as HIV and AIDS. Having a weakened immune system 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, or to treat auto-immune diseases such as arthritis or colitis)
  • 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 an 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 that occur in chickenpox or shingles 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 episodes in the future increases.

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.

Chronic
Chronic usually means a condition that continues for a long time or keeps coming back.
Immune system
The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.
Liver
The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.
Obesity
Obesity is when a person has an abnormally high amount of body fat.
Veins
Veins are blood vessels that carry blood from the rest of the body back to the heart.

Your GP can usually diagnose cellulitis by assessing your symptoms and examining your skin.

Before making a diagnosis, your GP may want to rule out other conditions that can lead to your skin becoming 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.

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. Special arrangements are sometimes made to allow antibiotic injections to be given in the patients home.

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 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 known as erythromycin can be used.

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 will be given a combination of two different antibiotics: usually doxycycline or ciprofloxacin in combination with flucloxacillin or erythromycin.

When you first start taking the antibiotics, you may notice that your skin becomes redder. This is usually only a temporary reaction, and the redness should start to fade within 48 hours.

Contact your GP immediately if your symptoms get worse 48 hours after taking the antibiotics, or you develop additional symptoms, such as a high temperature or vomiting.

Self-care

If you have cellulitis, there are things you can do at home to ease your symptoms and speed up your recovery.

Drink plenty of water to prevent dehydration. If your leg is affected by cellulitis, keep it raised. 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 painkiller may ease your symptoms. Paracetamol and ibuprofen are suitable for cellulitis.

Treatment at hospital

If you need to be admitted to hospital for treatment, you will be given antibiotics directly into your vein through an injection or a drip (known as intravenous antibiotics).

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.

Antibiotics
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Fever
A high temperature, also known as a fever, is when someone's body temperature goes above the normal 37°C (98.6°F).
Kidney
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.
Liver
The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.

Blood poisoning

If the bacteria that infect your skin and tissue enter your bloodstream, they could cause blood poisoning (septicaemia). Symptoms of blood poisoning may include:

  • high temperature (fever) of 38ºC (100.4ºF) or above
  • rapid heart beat
  • rapid breathing
  • low blood pressure, which will make you feel dizzy when you stand up
  • changes 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 112 for an ambulance.

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.

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 112 immediately for an ambulance.

The best way to protect your child against meningitis is to make sure they have all their childhood vaccinations, which include :

  • haemophilus influenzae type b bacteria
  • group C meningococcal bacteria
  • Pneumococcal vaccine

The vaccine and the booster provide immunity against three leading causes of meningitis in children:

  • haemophilus influenzae type b bacteria
  • group C meningococcal bacteria
  • Pneumococcal bacteria

Ask your GP if you are unsure whether your child's vaccinations are up to date.

Abscess
An abscess is a lump containing pus, which is made by the body during infection.
Antibiotics
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Heart valves
Heart valves are four sets of flaps that control the direction that blood pumps around the heart.
Vein
Veins are blood vessels that carry blood from the rest of the body back to the heart.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

Browse Health A-Z