What Is Cellulitis?

Yesterday it was a small patch of redness. Today it is bigger, warmer, and sore to touch — so what is going on? In many cases, the answer is cellulitis. The short video above, "Cellulitis," runs for just over two minutes and sets out what this infection is and why it deserves prompt attention. Here, we walk through the questions people usually ask when they first hear the word.

What exactly is cellulitis?

As the anchor video explains — it even gives you the pronunciation, "sel-u-LIE-tis" — cellulitis is a common, potentially serious bacterial skin infection. You are not looking at a rash sitting on the surface. The infection involves the skin itself, and it announces itself as a swollen, red area that feels hot and tender when you touch it. That combination — spreading redness, warmth, swelling, and soreness — is the picture to hold in mind, because each part of it matters when a clinician examines you.

Where does it appear, and who catches it from whom?

The lower legs are the most commonly affected area, the video notes, though cellulitis can occur anywhere on your body or face. And here is a point that often surprises people: cellulitis isn't usually spread from person to person. You do not generally catch it by touching someone who has it. It is an infection of your own skin that develops and then, if it is not treated, expands — which is why a patch that looked minor in the morning can look noticeably larger by the evening. For a setting where cellulitis is one end of a wider spectrum, the site's "Diabetic Foot Infection Treatment" video shows how foot infections in diabetes can range from simple, superficial cellulitis through to much deeper infection.

Why do clinicians take a spreading patch seriously?

Because of where the infection can go next. The anchor video explains that cellulitis might affect only your skin's surface — or it might also involve the tissues underlying your skin, and can spread to your lymph nodes and bloodstream. That possibility is the whole concern. An infection that reaches the bloodstream is a body-wide emergency; our article on what sepsis is explains how a localised infection can escalate into one that affects the whole body. Cellulitis sits at the earlier, more treatable end of that story — which is exactly why speed matters.

So what should you do if you suspect it?

The anchor video is direct about this: left untreated, the spreading infection can rapidly turn life-threatening, and it is important to seek immediate medical attention if cellulitis symptoms occur. So this is not a "wait a few days and see" condition. If you notice a red, hot, tender, swollen area of skin — particularly on a lower leg — and especially if it is spreading, getting examined the same day is the sensible move. A webpage can help you recognise the pattern; it cannot examine your leg, judge how deep the infection goes, or decide what treatment you need. That judgement belongs to the clinician in front of you.

Frequently Asked Questions

Is cellulitis contagious?
Not usually. The anchor video notes that cellulitis isn't usually spread from person to person — it is an infection within your own skin, rather than something you typically catch from someone else.

Which part of the body does cellulitis affect most often?
The skin of the lower legs is most commonly affected, according to the anchor video, though cellulitis can occur anywhere on the body or face.

When should cellulitis be treated as urgent?
Promptly, whenever you suspect it. The anchor video warns that an untreated, spreading infection can rapidly turn life-threatening and can reach the lymph nodes and bloodstream, so it advises seeking immediate medical attention if cellulitis symptoms occur.

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician and researcher.

Educational only — this article is general information about cellulitis, not medical advice and not a diagnosis. A spreading, red, hot, or tender area of skin should be examined promptly in person.