Granuloma annulare is a long-lasting rash that looks like a ring of small red or skin-coloured bumps.
The rash usually appears over the backs of your forearms, hands or feet. It tends to affect children and young adults, and is slightly more common in females.
What causes granuloma annulare?
In granuloma annulare, the dermis (the tissue underneath the top layer of skin, which is known as the epidermis) becomes hypersensitive and inflamed. It's not clear what causes the skin to react in this way.
The condition is sometimes associated with diabetes.
The rash is usually the only symptom of granuloma annulare, and most people with it are otherwise healthy. It may be slightly itchy, but it isn't usually painful.
There may be a number of rings that grow slowly until they're about 2.5-5cm (1-2 inches) across. They then become flatter and more purple in colour, before eventually fading.
In rare cases, the rash may spread all over the body, or there may be one or more firm lumps under the skin of the arms or legs (this is known as subcutaneous granuloma annulare).
Granuloma annulare usually disappears without treatment within two years, although it can sometimes last for many years and new rings may appear. It's not infectious or caused by allergies.
What to do
Contact your GP if you notice a ring anywhere on your skin that doesn't go away within a few weeks. They'll be able to rule out other possible causes, like a fungal infection.
Because granuloma annulare is harmless, you may not need any treatment for it. However, you may wish to consider treatment if the appearance of the rash is upsetting you.
How it's treated
There's no specific treatment for granuloma annulare and evidence for the use of medication is limited.
Strong steroid creams or ointments, or steroid injections directly into the rings, may help to clear up the rash. However, steroids must be used carefully, because long-term use can thin the skin.
Severe or widespread cases of granuloma annulare can be treated with ultraviolet light therapy (PUVA) or medicines that suppress the immune system, usually imiquimod, tacrolimus or pimecrolimus cream.
In some cases, cryotherapy (freezing the bumps with liquid nitrogen) may be recommended as a way of removing them and stimulating new skin growth. However, this type of treatment isn't always effective, and it can be painful and cause permanent scarring.