Cellulitis

Illustration of bacterial skin infection that causes cellulitis.

Cellulitis is a common infection of the skin and the soft tissues underneath the skin. Bacterial skin infections and soft tissue infections occur when bacteria invade broken or normal skin and start to spread under the skin and into the soft tissues. Infection results in inflammation, which is a process in which the body reacts to the bacteria. Inflammation may cause swelling, redness, pain, and/or warmth.

• People at increased risk for developing cellulitis include those with trauma to the skin or other medical problems such as the following risk factors:
  • Diabetes (high blood sugar)
  • Circulatory problems causing inadequate blood flow to the limbs (peripheral arterial disease)
  • Poor venous or lymphatic circulation (lymphedema), such as after surgical vein harvesting or varicose veins
  • Liver diseases, such as chronic hepatitis or cirrhosis
  • Iron overload conditions, such as hemochromatosis or conditions that require frequent blood transfusions
  • Skin disorders, such as eczema, psoriasis, infectious diseases that cause skin lesions such as chickenpox, athlete's foot, or severe acne

A number of factors can increase the chance that bacteria may invade the skin and cause infection. These risk factors include the following:

• A puncture wound or injuries that break the skin
• Infections related to a surgical wound
• Any breaks in the skin that allow bacteria to invade the skin (examples are chronic skin conditions such as eczema)
• Foreign objects in the skin
• Bacteria that typically cause cellulitis include group A Streptococcus and Staphylococcus aureus (also known as staph or staph infection). Some S. aureus infections are resistant to some antibiotics (for example, methicillin-resistant Staphylococcus aureus or MRSA) or are prone to causing abscesses or collections of pus in the skin.
• Infection of bone underneath the skin (An example is a long-standing open wound that is deep enough to expose the bone to bacteria. Sometimes this occurs in people with diabetes who have lost sensation or have poor blood flow in their feet.)
• Swelling in the leg or arm from varicose veins or after surgery on veins or lymph nodes (lymphedema) is a common risk factor for streptococcal cellulitis.
• Dog or cat bites or licking can cause severe cellulitis due to Pasteurella or Capnocytophagia, especially in diabetics or people with poor immune function or absence of the spleen (asplenia) or splenectomy, surgical removal of the spleen.
• People with liver disease or iron overload are at risk for cellulitis from exposure to mud, soil, or water (freshwater or seawater). Vibrio vulnificus, Pseudomonas, and Aeromonas are common bacteria in such situations. Tell the doctor if you have liver disease or if there has been exposure to soil, freshwater, or saltwater.
• Erysipelas is a superficial streptococcal infection of the face that appears similar to cellulitis.

Cellulitis is defined as a syndrome of swelling of the skin and subcutaneous tissues, tenderness to touch, and redness of the skin with a diffuse border. It can occur in almost any part of the body.

On the head and face, the most common areas are the eye, eyelid, ear, and nose or nasal area.

• Around the eye and eyelid, it is called orbital cellulitis.
• Around the nasal area and cheeks, erysipelas is a syndrome of redness and tenderness like cellulitis but is more superficial.
• The skin in erysipelas looks puffy and slightly pitted, with an orange peel appearance, and the redness has well-defined borders.
• This appearance is helpful in choosing antibiotics because it is almost always caused by strep bacteria.

Other common areas of cellulitis are the arm, hand, leg, ankle, and foot. Most commonly, it occurs in areas that may have been damaged or are inflamed for other reasons, such as inflamed injuries, contaminated cuts, or areas with poor skin hygiene. Bad circulation from poor vein function or peripheral arterial disease is a common cause of cellulitis.

The common symptoms and signs of cellulitis are as follows:

• Redness of the skin or red rash
• Red streaking of the skin or broad areas of redness
• Swollen skin
• Warm skin
• Skin pain or tenderness
• Drainage or leaking of yellow clear fluid or pus from the skin; large blisters may occur
• Tender or swollen lymph nodes near the affected area, or red streaks extending from the red area (lymphangitis)
• Fever, chills, and malaise can result if the condition spreads to the body via the blood.
• Pus or a blackened area surrounded by redness, pain, and warmth may be a deep abscess or MRSA (type of staph infection). Very often, MRSA cellulitis is confused with the bite of a brown recluse spider, which can appear very similar.

Check the skin often. Cellulitis can worsen quickly. Call your doctor or go to an emergency room if you have any of the following signs or symptoms of cellulitis:

• Fever or chills
• Redness on the skin
• Red streaks on the skin
• Increased warmth in the affected area
• Swelling
• Tenderness
• Drainage from the skin
• You have poor circulation.

Go to the hospital's emergency department if you have any signs or symptoms of the following:

• High fevers or chills
• Nausea and vomiting
• Obvious enlargement or hardening of the reddened area
• Increasing pain, blisters, or pus
• Numbness of the reddened or tender area when lightly touched (this can suggest necrotizing fasciitis)
• A dark or blackened area that is tender, red, swollen, and warm (necrotizing fasciitis)
• Signs or symptoms around the eye with loss of vision or inability to move the eye (orbital cellulitis)
• Signs or symptoms around the ear with hearing loss
• Signs or symptoms around the nose and face
• Other medical problems that may be affected by even a minor infection, such as diabetes, liver disease, iron overload, or poor immune function (immune deficiency or immunosuppression)

Most primary care doctors (including family practice doctors, internal medicine doctors, pediatricians, and geriatricians) or emergency-medicine doctors can treat cellulitis.

• Most treatment will occur as an outpatient. If the condition is severe, these doctors may need to provide treatment in the hospital.
• A dermatologist (skin specialist) treats many types of complicated skin conditions and can treat cellulitis.
• However, dermatologists are very specialized, and most people first see a primary care or emergency-room doctor for the treatment of cellulitis.
• If you require hospitalization for severe cellulitis, an infectious-disease specialist and a surgeon may be consulted to assist in treatment.
• An ear, nose, and throat surgeon may be consulted for ear cellulitis if malignant otitis externa is suspected.

Most likely, the doctor will make the diagnosis from a medical history and physical examination.

• The doctor may also draw blood for testing if he or she feels the infection is severe enough to be in the bloodstream or to check for an elevated white blood cell count.
• The doctor also may order an X-ray or other imaging study of the area if there is concern that a foreign object is in the skin or that bone underneath is infected.
• The doctor may try to draw fluid from the affected area with a needle and send the fluid to the laboratory for a culture.

• If the infection is not too severe, you can be treated at home. The doctor will give you a prescription for oral antibiotics to take by mouth. The duration of treatment is usually about a week to 10 days. Do not stop treatment early; finish all of the medication you are prescribed unless the doctor tells you to stop.
• The doctor may use intravenous (IV) or intramuscular antibiotic injections in these situations:
  • If the infection is severe
  • If you have other medical problems
  • If you have a weakened immune system
  • If you are very young or very old
  • If the cellulitis involves extensive areas or areas close to important structures (for example, infection around the eye socket)
  • If the infection is not improving or worsens after taking oral antibiotics for two to three days
• You may need hospitalization if the infection is advanced, extensive, or in an important area, like the face. In most of these cases, IV (intravenous) antibiotics need to be given until the infection is under good control (two to three days) and then you can be switched to oral medications to be taken at home. In some cases, the duration of treatment may need to be prolonged, especially if the infection is responding slowly.

• Cellulitis must be treated with antibiotics. Home remedies alone do not cure it but can help speed healing.
• Rest the area of the body involved.
• Elevate the area of the body involved. This will help decrease swelling and relieve discomfort.
• Use over-the-counter pain relievers such as acetaminophen (Tylenol). This will decrease the pain, as well as help, keep the fever down.

Antibiotics are prescribed by mouth (oral) or by injections. Be sure to tell your health care provider about any reactions you may have had in the past to antibiotics. Several antibiotics may be prescribed for cellulitis, alone or combined, depending on the suspected bacteria and the seriousness of the infection. Common ones include

• doxycycline (Vibramycin), ciprofloxacin (Cipro), clindamycin (Cleocin), cefazolin, dicloxacillin, amoxicillin/clavulanic acid (Augmentin), cefuroxime by mouth (Ceftin), cephalexin, sulfamethoxazole/trimethoprim (Bactrim), amoxicillin (Amoxil), nafcillin, cefuroxime (Zinacef), piperacillin/tazobactam (Zosyn), ampicillin/sulbactam (Unasyn), vancomycin, and ceftriaxone (Rocephin).

• Rarely, a soft-tissue infection may need surgery.
• An abscess, or collection of pus in the tissue, may need to be opened surgically to allow drainage.
• Dead tissue may need to be cut away to stop the infection from progressing or to allow healing.

Once you leave the doctor's office, be sure to take all the antibiotics prescribed.

• Do not stop taking the antibiotics early unless the doctor instructs you to stop.
• The doctor may want to see you in two to three days to make sure that the cellulitis is improving.

Severe cellulitis may cause the spread of bacteria into the bloodstream (sepsis, or blood poisoning), which can be life-threatening. There are some very serious complications that are fortunately very rare, but awareness can be lifesaving.

The infected soft tissue may die (gangrene). Very severe cellulitis and tissue death may rarely spread deep inside to the muscle (necrotizing fasciitis).

• Necrotizing fasciitis or gangrene is an emergency. It is life-threatening if the dead tissue is not surgically removed (debridement or amputation). Necrotizing fasciitis may be present even if the surface of the skin does not look dead, so it is important to recognize the signs and symptoms of this emergency. Signs and symptoms include worsening fevers even with antibiotics, deep pain that is worse than the infection appears, hardening of the tissues under the skin, and numbness of the surface of the skin.

Cellulitis around the eye is serious.

• If cellulitis is only in the tissues in front of the eye socket (orbit), it is preseptal cellulitis, and oral antibiotics may be enough to cure it.
• If the cellulitis is behind the eyeball or in the eye socket, it is orbital cellulitis. Orbital cellulitis is an emergency and can cause permanent loss of vision or spread of infection into the brain (meningitis).
• This is especially life-threatening in people with diabetes, iron-overload diseases (hemochromatosis), or liver disease.
• Orbital cellulitis may require hospitalization and treatment by an ophthalmologist (eye surgeon) or an ear, nose, and throat surgeon.
• Signs and symptoms of orbital cellulitis include loss of vision and difficulty moving the eyeball.

External ear infections (swimmer's ear) in a person with diabetes may become cellulitis, with severe swelling of the external ear canal (malignant otitis externa). Malignant otitis externa may spread deep into the ear and the skull bone. This may cause permanent hearing loss. A diabetic with worsening external ear infection should seek urgent care. The diagnosis often requires a computed tomography (CT) scan to evaluate the skull around the ear. An ear, nose, and throat surgeon is often involved in treatment, but usually, it can be treated with antibiotics, and no surgery is needed.

The blood flow of the nose and upper lip drains back into the veins of the skull. Cellulitis around the nose may very rarely spread to cause infected blood clots in these veins (cavernous sinus thrombosis).

• This is life-threatening.
• Signs and symptoms of cavernous sinus thrombosis include headache, high fever, loss of consciousness, and bulging of one or both eyes.

• It is very important to keep your skin clean by practicing good personal hygiene.
• If you notice pain or discomfort from an area of the skin, check to see what it looks like. If it appears inflamed and progresses from one day to the next, you will most likely need treatment.
• Avoid situations that may injure your skin, especially if you have to swell from circulatory problems.
• If you have circulatory problems and the skin is dry, keep it moisturized to avoid cracking.
• Wear sturdy, well-fitting shoes or slippers with loose-fitting cotton socks. Avoid walking barefoot in areas where you do not have a good idea about what you are walking on, for example, in garages, on a littered beach, or in the woods.
• If you do injure your skin, wash the area with soap and water and check to make sure that the injury is getting better over the next several days.
• Certain injuries may be at greater risk factors for infection than others. You may need to have a tetanus vaccine. Be sure to contact your doctor if you have injuries such as these:
  • Animal or human bites
  • Puncture injuries deeper than a ½ inch, such as stepping on a nail
  • Crushed tissue that bleeds, burns that blister, frostbite, or deep injuries with dirt in them
  • Injuries in contact with fresh water or seawater
• Find out if you have diabetes or other significant medical conditions, such as liver or kidney disease. These conditions may be present without symptoms. Follow your doctor's instructions for the management of these conditions.
• Talk to your doctor if you have swelling in your limbs that does not go away.

Most people respond to the antibiotics in two to three days and begin to show improvement. In rare cases, cellulitis may progress to a serious illness by spreading through the bloodstream. Some forms of severe cellulitis may require surgery and leave a person with scarring. Rarely, cellulitis can be life-threatening.