Erythema annulare centrifugum (EAC) is a rare skin rash.
The rash has small red bumps that spread out from a central area. The bumps often form a ring-like pattern, but may spread into irregular shapes. The center area may lighten up. You may have more than one area of rash.
EAC usually shows up on the thighs or legs. But it can appear elsewhere, including on the face, trunk, and arms.
The rash may appear for no known reason and go away on its own, or it may be a sign of an underlying problem. It may appear at the same time that you have an allergic reaction to food or drugs, or after a spider or tick bite.
EAC may also be a sign of an infectious disease. In about 13 percent of cases, there is an underlying illness or infection. Rarely, it may be a sign of cancer.
The average age of onset is 49 years, but EAC rash can appear at any time of life, from infancy on.
Other names for the EAC rash are:
- superficial or deep gyrate erythema
- erythema perstans
- palpable migrating erythema
The name EAC comes from the Latin words for red rash (erythema), ring-like (annulare), and spreading from the center (centrifugum).
The EAC rash usually begins as a small pink or red spot that gradually enlarges.
In some people, the rash may itch or sting, but often there are no symptoms.
As the rash spreads outward, it may take on the appearance of rings, like a bull’s-eye. But it can also appear as a uniform circle of redness, or an irregular shape. The edges of the rings are usually raised and may be slightly scaly.
Each rash spot can range in size from one-quarter inch to more than three inches.
The exact cause of EAC rash is not known. It can be a sign of a hypersensitivity reaction or an underlying disease. Rash triggers include:
- food allergy
- arthropod bite (insect, tick, spider)
- infectious disease (viral, bacterial, parasitic, fungal)
- endocrine or immune system disorder, including Graves’ disease, Hashimoto’s thyroiditis, Sjögren syndrome, and autoimmune progesterone dermatitis
- Hodgkin’s and Non-Hodgkin’s lymphoma
- acute leukemia
- multiple myeloma
- other cancers (nasopharyngeal, prostate, breast, ovarian)
Your doctor will determine if your rash is EAC by a visual and physical examination, combined with a medical history.
You may have other diagnostic tests to rule out other possibilities, and to find out if the rash is the result of an underlying disease. These may include basic blood work and possibly a chest X-ray.
A review of the drugs you’re taking can help determine if you may be having an allergic drug reaction. Drugs that may cause the EAC rash include:
- gold sodium thiomalate
If you have other symptoms, such as fatigue, your doctor may refer you to a Lyme disease specialist. Be aware that the common ELISA (enzyme-linked immunosorbent assay) and Western blot tests are not a reliable indicator of absence of Lyme disease.
This cycle of clearing up and reappearance can go on for months or years. The average duration is one year.
There is no proven treatment. Your doctor may prescribe a corticosteroid (cortisone) ointment or cream for relief if you have itching.
Alternative treatments reported to be successful in some cases include:
- the oral antibiotics metronidazole and erythromycin
- hyaluronic acid
- calcipotriol, a vitamin D derivative
If your rash is a result of an underlying condition, such as an infection, it will usually clear up once the infection is cured.
Home remedies for itchiness or inflammation that may provide some relief include:
- aloe vera gel
- baking soda (made into a paste with a few drops of water)
- colloidal oatmeal (available over-the-counter, or you can prepare your own)