Erythema annulare centrifugum (EAC) is a skin condition that produces slowly expanding ring-shaped red patches, typically on the trunk, thighs, or buttocks. The rings grow outward at roughly 2 to 3 mm per day, clearing in the center as they expand, which gives them a distinctive target-like or arc-shaped appearance. EAC is uncommon, tends to peak around age 40, and affects women roughly twice as often as men.
What the Rash Looks Like
EAC starts as small pink or red bumps. Over days, each bump expands outward and flattens, leaving normal-looking skin in the center while the border remains raised and pink. The result is an expanding ring or partial arc that can reach several centimeters across. Some people develop a single ring; others have multiple rings or overlapping wavy shapes (called polycyclic plaques).
The hallmark feature is a fine line of peeling skin along the inner edge of the ring, known as a “trailing scale.” Instead of the scale sitting on top of the raised border (as you’d see with ringworm), it trails behind the advancing edge on the inside. Not every ring shows this scale, but when it’s present, it’s one of the strongest visual clues for EAC. The surface of the rings generally stays smooth, without blisters or crusting.
Superficial vs. Deep Forms
Dermatologists recognize two variants. The superficial form is more common and produces the classic picture described above: slightly raised rings with trailing scale and, in many cases, mild itching. The deep form looks different. Because the inflammation sits deeper in the skin, the rings are firmer, more raised, and lack the trailing scale entirely. Deep EAC also tends not to itch. A skin biopsy can distinguish the two, revealing a characteristic “coat-sleeve” pattern of immune cells wrapped tightly around small blood vessels.
What Triggers It
EAC is considered a hypersensitivity reaction, meaning the skin is reacting to some internal or external trigger rather than being attacked by an infection itself. The list of possible triggers is long and includes fungal infections (especially dermatophytes like athlete’s foot or jock itch), bacterial and viral infections, medications, hormonal changes during pregnancy, and autoimmune conditions. In many cases, no trigger is ever identified.
A small but important subset of EAC cases is linked to underlying cancer. This association is sometimes called paraneoplastic erythema annulare centrifugum eruption, or PEACE. In a case series of 40 paraneoplastic cases, about 63% were tied to blood cancers (most often leukemia or lymphoma) and 37% to solid tumors. This link is uncommon overall, but it’s one reason dermatologists may order bloodwork or imaging when EAC appears without an obvious trigger, especially in older adults or when the rash is widespread or resistant to treatment.
How It’s Diagnosed
Diagnosis relies on the rash’s appearance combined with a skin biopsy when needed. Several other conditions produce ring-shaped skin lesions, and ruling them out is an important part of the process:
- Ringworm (tinea corporis) produces itchy, scaly rings that look similar but will test positive for fungus on a skin scraping. EAC will not.
- Erythema migrans (Lyme disease) creates a single expanding red patch at the site of a tick bite, often reaching much larger sizes than EAC rings.
- Granuloma annulare forms smooth, rubbery, raised rings without any scale.
- Erythema multiforme produces classic targetoid lesions, but these favor the hands and feet and have a distinct three-zone color pattern.
- Erythema gyratum repens has a dramatic “wood-grain” pattern and is more strongly associated with internal malignancy.
Under the microscope, EAC shows immune cells clustered tightly around blood vessels in the dermis. Despite this, the vessel walls remain intact, so it’s classified as a pseudo-vasculitis rather than a true vasculitis.
Treatment and What to Expect
Individual rings of EAC typically heal on their own within days to weeks and resolve without leaving scars or permanent marks. The challenge is that new rings often keep appearing. In a study of 66 patients, the average disease duration was 2.8 years, though some people deal with recurring episodes for a decade or longer. One case series documented disease durations ranging from 1 to 30 years, with a median of 12 years. Some patients experience annual flares that show up around the same time each year.
When a specific trigger is identified, treating or removing it can resolve the rash. If a fungal infection elsewhere on the body is driving the reaction, clearing the fungus often stops new rings from forming. When the rash is bothersome, topical steroid creams can reduce inflammation and itching, particularly for the superficial form. For persistent or widespread disease, stronger anti-inflammatory treatments may be considered, though there is no single standard therapy that works for everyone.
The condition itself is benign. The rings are not contagious and don’t cause internal harm. The main concern is cosmetic frustration from recurrent episodes and, in a minority of cases, the possibility that the rash signals something else going on internally. If EAC keeps recurring without an obvious cause, a thorough workup for underlying conditions is reasonable.