AUTHOR: Marc Mitnick DPM

Podiatric Medical Review Board

--> cellulitis

Cellulitis occurs when one or more types of bacteria enter through a crack or break in the skin and an infection ensues. The condition manifests itself as a "redness" and "swelling" which is the cardinal signs of an infection.


In the foot, sources of breaks in the skin and resulting infections include:

  • heel fissure
  • ulcers
  • burns
  • insect bites
  • trauma
  • cuts
  • scratches
  • surgical incision-possibly the most common risk in all surgery is the chance of infection.
  • athletes foot-a secondary bacterial infection is very common with athletes foot which is one of the reasons that even if you have a mild case of athletes foot it should be treated.
  • dry flaky skin
  • swollen skin
  • thrombophlebitis-in this case cellulitis can develop with no actual break in the skin.

For reasons just stated, cellulitis therefore is very common in the foot and lower leg. This condition is caused by bacteria, generally streptococcus or staphylococcus, but there can be other bacteria mixed in. This is especially true in diabetics.

People whose immune systems are weakened for any reason (including from chemotherapy for cancer or other immune-suppressing drugs) and those with diabetes or AIDS are at highest risk for developing infections.


The problem usually presents itself locally as swelling, redness and tenderness at the site of infection. Additionally, systemically, a person may also have fever, chills, elevated oral temperature and swollen lymph nodes, which is usually seen in advancing cases.

In more severe cases untreated cellulitis can get into the blood stream leading to systemic manifestations such as kidney failure or heart failure. Locally, the soft tissue infection may invade adjacent bone resulting in osteomyelitis.

Below is a picture of cellulitis in the foot.

foot infection

To further complicate matters, other problems will cause similar symptoms in the foot, these include:


SIMPLE INFECTIONS-Treatment is predicated on the severity of the condition. In a case of a healthy individual who has developed cellulitis secondary to an infected ingrown nail and it only extends an inch or so from the infection site, removal of the offending portion of nail and topical antibiotic medication is all that is usually necessary.

Small localized infections may be treated with simple cleansing with soap and water, along with a dressing which includes a topical antibiotic ointment.

SEVERE INFECTIONS-In the patient who may be diabetic, may be on immuno-suppressive drugs, a wound has to be evaluated for infection. General guidelines as to whether or not a wound requires oral antibiotics include the degree to which there is cellulitis (redness that extends way beyond the borders of the wound), an increase in pain in the area, poor quality of granulation tissue in the wound, increased drainage from the wound, tunneling (channels leading deeper into the tissue) and odor. If the patient has an elevated oral temperature, that too has to be considered.

cellulitis and antibiotics

If the criteria is met an oral antibiotic is prescribed. Your doctor will normally start you on an oral antibiotic that is known as a broad spectrum antibiotic; an antibiotic that kills a wide variety of bacteria. At the same time, your doctor will take a sample of drainage in the wound and send it out to a laboratory to find the specific organisms causing your infection. Most skin infections are either staph aureus (most common) or strep infections. In these instances a first generation cephalosporin or perhaps a penicillin type antibiotic will be prescribed.

Complicating the bacteria picture, in recent years are the methicillin resistant staph aureus bacteria (MRSA). They do not respond to the broad spectrum drugs just mentioned. A popular option for MRSA is doxycycline 100mg twice a day for upwards of ten days.

Pseudomonas infections are also fairly common in skin infections of the foot and lower leg. Generally the signs of infection will not be as severe as seen with staph and strep. The drug of choice here is the group of antibiotics known as quinolones. It is worth mentioning that quinolones have a tendency to cause tendon ruptures, primarily the Achilles tendon, so it is important to be aware of this, if you are presently taking this medication.

The key here is to take all of the antibiotics no matter how good the foot may look after a day or so. Typically, what happens is that the infection begins to look and feel much better in a couple of days and the patient will stop taking the antibiotics only to experience what is known as a rebound phenomenon where the redness and infection return, thus delaying the time it takes to ultimately clear up the problem.

When your doctor suspects an infection that requires an oral antibiotic, he or she will initially start you on one of the above mentioned drugs. In addition, your doctor has to find out exactly what organism(s) is causing your infection. This is done with what is known as a wound culture. In years gone by your doctor would swab the top of the wound with a Q-tip like swab and send that to the lab to find out which bacteria is involved. That thinking has changed.

The real organisms that are causing your infection generally lie deeper in the wound. The organisms that lie on top of the wound are known as normal colonized bacteria (they are just bacteria sitting in the wound). The proper way to culture a wound is to actually clean the surface of the wound with an antiseptic, then swab the wound as deep as the swab can be placed without torturing the patient. The more recent thinking is to actually remove a small piece of deep tissue and send that out for testing as that is the "best" way to get an accurate reading. Once the results come back from the lab, your doctor may switch the antibiotic you are taking to a different one that is more specific for the bacteria found in the wound culture.

Locally, the affected area will also be treated with topical medication and a dressing to prevent re-infection. If there is an underlying cause such as athletes foot , fissuring , dryness in the skin or foot ulcers , they all have to be addressed otherwise the risk of re-infection remains high.

Unfortunately, simple infections that are improperly treated many times will turn into a severe infections. Depending on the overall health status of the patient, bed rest, intravenous antibiotics and possibly hospitalization may all be necessary.

Cellulitis is not a condition that can be self treated. It requires proper medical care.


Mayo Clinic


American Academy of Dermatology

See also....wound care

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