Cellulitis is a bacterial infection that affects multiple layers of skin, and particularly the deeper layers. In many cases, a cellulitis infection penetrates further than just the dermis, affecting subcutaneous fat as well. And often, the lymphatic system becomes involved, leading to additional symptoms, including fever, fatigue and malaise. If lymph nodes are involved, red streaks may spread out from the site of the infection, displaying the inflammatory nature of the condition.

In all cases of cellulitis, the characteristic symptoms are redness and inflammation at the infection site, which is usually found on the legs or face, though cases of cellulitis can appear anywhere. Cellulitis is typically painful when the infected area is touched. The infection area may not be sharply defined, often with a diffused redness spreading out from the infection site.

Because cellulitis is a general skin infection, cases differ greatly in their severity. Most cases of cellulitis can be quickly and easily treated with a healthcare provider’s support. However, cellulitis can become a serious health threat if it is allowed to spread or if it develops close to the eye or in the mouth.

What causes cellulitis and what are its risk factors?

Cellulitis can be caused by a variety of bacteria, but streptococci and Staphylococcus aureus represent the lion’s share of cases. Both bacteria types exist in extremely large concentrations on the body, but don’t present a threat to people unless they are able to enter the skin. Cellulitis can also develop on the face, and when it does, it’s almost always due to a dental infection. This is a more serious form of cellulitis, given the proximity to the eyes, throat and nasal passages. In rare cases, a form of cellulitis known as Ludwig’s angina (an infection of the submandibular space) can develop following a dental infection. Ludwig’s angina is a serious medical condition, capable of producing life-threatening symptoms if not addressed right away.

There are numerous risk factors that can increase the chances of developing cellulitis. They include:

1. Genetic factors – The genetic link to cellulitis prevalence is not completely understood, but there is some evidence that suggests that genetics play a large role in what kind of bacteria are most prevalent on a patient’s body. Those with greater amounts of strep and Staph are more likely to develop cellulitis.

2. Breaks in the skin – Cellulitis only develops when there is a break in the skin for strep or Staph to enter. This break is often not visible, so infection may develop even where there is no obvious opening. There are many predisposing conditions for cellulitis, including insect bites, animal bites, blisters, rashes, athlete’s foot, eczema, dry skin, recent tattoos or surgery and the use of intravenous drugs. Any of these can produce a significant enough skin wound to result in infection.

3. Conditions that suppress the immune system – Patients harboring a weakened immune system will be less able to fight off the bacteria once it enters the body. Instances of cellulitis that develop in people with weaker immune systems would often be no threat to a healthy individual.

The elderly, therefore, are at an increased risk of cellulitis, as well as people suffering from diseases that affect the immune system, like HIV/AIDS or diabetes.

People taking immunosuppressive drugs are also at an increased risk of cellulitis.

4. Conditions that produce additional risks on the skin – Some illnesses present with skin symptoms that make it easier for strep or Staph to enter the body. Chicken pox and shingles, for example, produce skin blisters that eventually burst open and create gaps in the epidermis through which bacteria can enter. Other conditions that produce skin swelling, like lymphedema, make it easier for bacteria to penetrate the epidermis.

Cellulitis can develop alongside other skin infections, like those involving methicillin-resistant Staphylococcus aureus, or MRSA. MRSA can cause the patient to develop abscesses, which represent a weak spot for other strains of strep or Staph to take advantage of.

5. Conditions that weaken circulation in the legs – A large portion of cellulitis cases develop in the legs. As such, reduced circulation in the legs is a significant risk factor, as the body cannot respond to potential infections as quickly. Some common diseases that reduce leg circulation include varicose veins and chronic venous insufficiency.

Diabetes, in addition to weakening the immune system, also damages circulation to the limbs, often to a profound degree. Diabetics are much more likely to develop cellulitis in the feet and due to poor glucose balance, bacteria that does enter the body is able to reproduce faster. Worse, if bacteria spreads to the bloodstream in diabetics, it will progress faster. In short, cellulitis demands immediate attention if the patient suffers from diabetes.

6. Dense living conditions – Cellulitis is contagious, so it rapidly spreads among dense populations and populations that share living or hygiene facilities. Nursing homes, college dormitories, military facilities and homeless shelters are common hotspots for cellulitis infections.

Treating cellulitis

In about 95 percent of patients, cellulitis will disappear within seven to 10 days, as long as it is treated. While most cases of cellulitis will run their course without treatment, going without treatment is a gamble, especially in patients that have other risk factors. This includes the very young and elderly. Immediate medical attention is also indicated if the following conditions are present:

  1. The infection is close to the eyes or spreads to the hands or feet.
  2. The infection is spreading rapidly or is covering a large part of the body.
  3. The infection is producing other symptoms, like fever, fatigue or malaise.
  4. The infection gets worse even after taking antibiotics for a few days.

Treatment can be performed by a healthcare provider and normally involves oral antibiotics to treat the infection. Pain relief drugs may be prescribed, though severe pain will require further examination, as it may be a sign that tissue death is present. If the cellulitis has resulted in an abscess, the healthcare provider may drain it. Keeping the infection elevated can also help with resolving it.

Cellulitis may appear harmless, but it should be examined by a healthcare provider who can treat the infection and ensure it doesn’t progress to something worse.