Dr. Greene`s Answer:
When ringworm is treated with an appropriate antifungal medication, such as Lotrimin, improvement is usually seen within 7 to 10 days. Treat it for at least one week following the clearing of the rash to make sure that all of the fungus is gone.
If the condition does not go away with 4 weeks of treatment, then it was probably not ringworm in the first place.
Many other skin conditions look similar enough to ringworm (ringworm look-alikes) for the diagnosis to be commonly confused.
Ringworm Look-Alikes: Granuloma
Granuloma annulare is a common skin condition with raised, flesh-colored bumps that appear in a ring. It may occur on any part of the body (though most commonly on the sides or backs of the hands or feet) and is most often localized to one area. The bumps may be red at the beginning, but this disappears as the ring forms. There is no itching or scaling. The rings vary in size from about 1/4 inch to 2 inches in diameter.
No one knows for certain what causes granuloma annulare. It is not an infection and is not contagious. I believe it is probably a slow hypersensitivity reaction that some individuals develop to different types of minor trauma. It may, however, be related somehow to diabetes and thyroid disease. Most children with granuloma annulare are healthy and don’t go on to develop diabetes or thyroid problems, but these do occur more commonly in people who form these rings than in those who don’t, especially if the rash is widespread.
Granuloma annulare usually disappears spontaneously within several months of appearing (though it can take years). In almost half of cases the ring comes back for a while, usually at the original site. Sometimes localized lesions may respond to topical steroid ointments. When lesions are widespread, some physicians recommend treating this condition with steroid injections, freezing treatments (cryotherapy), UV light therapy or even stronger medications. All of these treatments may have side effects, so a thorough discussion with your doctor is needed before pursuing any form of treatment. Since the ring is usually not bothersome, and usually disappears on its own, I do not routinely recommend treatment. Often these rings will disappear following a small injection of sterile saline, so if treatment is chosen, I would consider this simple, safe method.
Ringworm Look-Alikes: Nummular Eczema
Nummular eczema is another common skin condition that is often mistaken for ringworm. The word nummular comes from the Latin word “coin,” and this rash is named so because it is a coin-shaped patch of dry, scaly skin. Itching is variable, and some people also describe a burning-like sensation. Common triggers for development of nummular eczema include medications, dry or damaged skin, bug bites, and contact with metals like nickel. Nummular eczema is aggravated by bathing, soaps, and irritants such as wool. Treatment involves limited bathing, generous use of alcohol-free moisturizers, and topical steroid creams. This can keep the patch under control, but it is not unusual for the condition to flare up again at the original site.
Occasionally patches of nummular eczema disappear when someone is taking an antibiotic for some other reason. Bacteria can invade the skin in these dry, scaly areas. If a patch of nummular eczema is stubborn, try treating with an antibiotic ointment.
Ringworm Look-Alikes: A Host of Less Common Culprits
Other conditions that occasionally look like ringworm include seborrhea, psoriasis, pityriasis, contact dermatitis (such as poison oak), drug reactions, tinea versicolor, vitiligo, erythema migrans (a rash seen in Lyme disease), and even lupus. Your physician can differentiate these from ringworm by a skin scraping or biopsy, if necessary.
Your question, Kyra, touches on an issue of profound importance. The take-home lesson is that a “feedback loop” is a critical part of your relationship with a doctor. When a doctor looks at a raised ring on the skin (or any condition), it is appropriate to make the most likely diagnosis based on the available information (and any testing that might be indicated). If things don’t improve as expected, make sure to tell your doctor, so that this new information can be used in setting a course from here.
This living cycle of observation and reevaluation allows the most accurate insight into the mysterious workings of Jerimie’s unique body. Whatever issues arise with his health, let your experience with this ring remind you to keep the loop connected.
Do you need more information on ringworm look-alikes? Let us know below.
References and Resources
Robinson CA, et al. Nummular Dermatitis. [Updated 2022 Oct 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan.
Piette EW, et al. “Granuloma annulare: Pathogenesis, disease associations and triggers, and therapeutic options.” J Am Acad Dermatol 2016;75:467-9.