Cellulitis is a bacterial infection involving
the skin. It specifically affects the dermis and subcutaneous fat. Signs and symptoms include
an area of redness which increases in size over a couple of days. The borders of the
area of redness are generally not sharp and the skin may be swollen. While the redness
often turns white when pressure is applied this is not always the case. The area of infection
is usually painful. Lymphatic vessels may occasionally be involved and the person may
have a fever and feel tired. The legs and face are the most common site
involved, though cellulitis can occur on any part of the body. The leg is typically affected
following a break in the skin. Other risk factors include obesity, leg swelling, and
old age. For face infections a break in the skin beforehand is not usually the case. The
bacteria most commonly involved are streptococci and Staphylococcus aureus. In contrast to
cellulitis, erysipelas is a bacterial infection involving the more superficial layers of the
skin, presents with an area of redness with well-defined edges, and more often is associated
with fever. More serious infections such as an underlying bone infection or necrotizing
fasciitis should be ruled out. Diagnosis is usually based on the presenting
signs and symptoms with cell culture rarely being possible. Treatment with antibiotics
taken by mouth such as cephalexin, amoxicillin or cloxacillin is often used. In those who
are seriously allergic to penicillin erythromycin or clindamycin may be used. When methicillin-resistant
Staphylococcus aureus is a concern doxycycline or trimethoprim/sulfamethoxazole may, in addition,
be recommended. Concern is related to the presence of pus or previous MRSA infections.
Steroids may speed recovery in those on antibiotics. Raising the infected area may be useful as
may pain killers. Around 95% of people are better after seven
to ten days of treatment. Potential complications include abscess formation. Skin infections
affect about 2 out of every 1000 people per year. Cellulitis in 2010 resulted in about
27,000 deaths worldwide that year. In the United Kingdom cellulitis was the reason for
1.6% of admissions to the hospital. Signs and symptoms
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. Causes
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.
Dental infections account for approximately 80% of cases of Ludwig’s angina, or cellulitis
of the submandibular space. Mixed infections, due to both aerobes and anaerobes, are commonly
associated with the cellulitis of Ludwig’s angina. Typically this includes alpha-hemolytic
streptococci, staphylococci and bacteroides groups.
Predisposing conditions for cellulitis include insect or spider bite, blistering, animal
bite, tattoos, pruritic skin rash, recent surgery, athlete’s foot, dry skin, eczema,
injecting drugs, pregnancy, diabetes and obesity, which can affect circulation, as well as burns
and boils, though there is debate as to whether minor foot lesions contribute.
Occurrences of cellulitis may also be associated with the rare condition hidradenitis suppurativa.
The appearance of the skin will assist 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.
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. Risk factors
The elderly and those with immunodeficiency are especially vulnerable to contracting cellulitis.
Diabetics are more susceptible to cellulitis than the general population because of impairment
of the immune system; they are especially prone to cellulitis in the feet, because the
disease causes impairment of blood circulation in the legs, leading to diabetic foot/foot
ulcers. Poor control of blood glucose levels allows bacteria to grow more rapidly in the
affected tissue, and facilitates rapid progression if the infection enters the bloodstream. Neural
degeneration in diabetes means these ulcers may not be painful and thus often become infected.
Those who have suffered poliomyelitis are also prone because of circulatory problems,
especially in the legs. Immunosuppressive drugs, and other illnesses
or infections that weaken the immune system, are also factors that make infection more
likely. Chickenpox and shingles often result in blisters that break open, providing a gap
in the skin through which bacteria can enter. Lymphedema, which causes swelling on the arms
and/or legs, can also put an individual at risk.
Diseases that affect blood circulation in the legs and feet, such as chronic venous
insufficiency and varicose veins, are also risk factors for cellulitis.
Cellulitis is also common among dense populations sharing hygiene facilities and common living
quarters, such as military installations, college dormitories, nursing homes, oil platforms
and homeless shelters. Diagnosis
Cellulitis is most often a clinical diagnosis, and local cultures do not always identify
the causative organism. Blood cultures usually are positive only if the patient develops
generalized sepsis. Conditions that may resemble cellulitis include deep vein thrombosis, which
can be diagnosed with a compression leg ultrasound, and stasis dermatitis, which is inflammation
of the skin from poor blood flow. Associated musculoskeletal findings are sometimes reported.
When it occurs with acne conglobata, hidradenitis suppurativa, and pilonidal cysts, the syndrome
is referred to as the follicular occlusion triad or tetrad.
Lyme disease can be misdiagnosed as staphylococcal- or streptococcal-induced cellulitis. Because
the characteristic bullseye rash does not always appear in patients infected with Lyme
disease, the similar set of symptoms may be misdiagnosed as cellulitis. Standard treatments
for cellulitis are not sufficient for curing Lyme disease. The only way to rule out Lyme
disease is with a blood test, which is recommended during warm months in areas where the disease
is endemic. Prevention
In those who have previously had cellulitis, the use of antibiotics may help prevent future
episodes. This is recommended by CREST for those who have had more than 2 episodes.
Treatment Treatment consists of resting the affected
area, in some cases cutting away dead tissue, and antibiotics. Flucloxacillin or dicloxacillin
monotherapy is often sufficient in mild cellulitis, but in more moderate cases, or where streptococcal
infection is suspected, then this course is usually combined with oral phenoxymethylpenicillin
or intravenous benzylpenicillin, or ampicillin/amoxicillin. Pain relief is also often prescribed, but
excessive pain should always be investigated as it is a symptom of necrotizing fasciitis.
Elevation of the affected area is also important. Epidemiology
Cellulitis as of 2010 results in about 27,000 deaths a year.
Other animals Horses may acquire cellulitis, usually secondary
to a wound or to a deep-tissue infection, such as an abscess or infected bone, tendon
sheath, or joint. Cellulitis from a superficial wound will usually create less lameness than
that caused by septic arthritis. The horse will exhibit inflammatory edema, which is
marked by hot, painful swelling. This swelling differs from stocking up in that the horse
will not display symmetrical swelling in two or four legs, but in only one leg. This swelling
begins near the source of infection, but will eventually continue down the leg. In some
cases, the swelling will also travel upward. Treatment includes cleaning the wound and
caring for it properly, the administration of NSAIDs, such as phenylbutazone, cold hosing,
applying a sweat wrap or a poultice, and mild exercise. Veterinarians may also prescribe
antibiotics. Cellulitis is also seen in staphylococcus and corynebacterium mixed infections in bulls.
See also Haemophilus influenzae cellulitis
Helicobacter cellulitis Tuberculous cellulitis