Red Patch of Rash

The skin is the largest organ in the human body, and because it’s outside bumping up against the environment all kinds of rashes can develop*. The causes of rash are many: infectious, allergic, and inflammatory to name a few. Sometimes they’re cancerous.

Diagnosing a rash right takes detective work. What was happening before the rash developed? What did the rash look like when it first started? What’s already been tried to treat it?

There are a lot of red patches of rash and just as many over-the-counter creams and ointments to treat them.  The art is matching them up correctly. The pattern can help make the diagnosis.
A small patch of rash with the skin looking uniformly red and irritated is often contact dermatitis or a bit of eczema. These rashes often respond to moisturizers and over the counter hydrocortisone ointments.

A ring-shaped rash of irritated skin around normal looking skin can be a sign of a fungal infection. As the fungus works its way outwards, the ring of infection grows leaving a healed center. Tinea corporis, the Latin-ed up name for this, often responds to over the counter anti-fungal creams like clotrimazole.

Rashes that appear infected and crusted are harder to pin down. Sometimes the infection is caused by staphylococcus or streptococcus bacteria and called impetigoCarefully soaking, removing the crust and applying over-the-counter antibiotic ointment like bacitracin may help, but more often, due to bacterial resistance, a prescription medication will be needed. Sometimes these infection are viral, like herpes or chicken pox.

*This post is not a substitute for medical care. Contact your doctor immediately for:

1. Any rash that appears blue or purple or looks like bruising or broken blood vessels.

2. Deep, tender red infections that may be caused by MRSA: methicillin-resistant staphylococcus aureas.

3. Moles that develop color changes.

4. Anything that concerns you.

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About Lisa M. Asta, MD

Lisa M. Asta, M.D. is board-certified by the American Board of Pediatrics and is a Fellow of the American Academy of Pediatrics, for which she is also a Media Representative (she has been interviewed for “Kids Health” on Health Radio, and quoted in Parenting Magazine, USA Today, and the New York Times, among other publications). She is a Clinical Professor of Pediatrics at the University of California at San Francisco and past pediatric chair at John Muir Medical Center in Walnut Creek. She graduated from Temple University School of Medicine and the Johns Hopkins University. Dr. Asta is also a writer whose fiction has appeared in Inkwell, Philadelphia Stories, Schuylkill, and Zeniada. Her essays have appeared in the Journal of the American Medical Association, Hippocrates, the San Jose Mercury News, and The New Physician Magazine. She is an occasional contributor to KQED public radio’s Perspectives series, and has written articles for Bay Area Parent, Valley Parent, Parents’ Press, and Parents Express, as well as online at,, and She wrote a chapter in The Field Guide to the Normal Newborn, ed. Gary Emmet, M.D. currently has two how-to videos for parents in production which feature Dr. Asta. For more on Dr. Asta’s writing, visit
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1 Response to Red Patch of Rash

  1. Pingback: Medicine Cabinet 101: Creams and Ointments | Casa Verde Pediatrics, Inc. Blog

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