A halo nevus is a mole that is pink or brown surrounded by an area of white or light skin. The halo is depigmented which means it has lost the normal skin pigment or color. 
The moles are usually seen in young people. The mole portion tends to flatten and may disappear completely. The white area may stay if the mole disappears, or the normal skin color may return.
Halo nevi are not dangerous or contagious, but they are sometimes a sign that something is wrong with the skin and as such should not be ignored.
What causes halo nevus to occur?
The condition occurs when the immune cells (which normally fight off infection) attack a mole for reasons unknown, but are sometimes seen in people with vitiligo.
Halo nevi may occur in patients with malignant melanoma, a more serious skin cancer.
Atypical moles are more common on people with halo nevi, and are thought to have an increased risk of turning cancerous.
What are the treatment options available?
Typically no treatment is necessary upon diagnosis. A yearly complete skin exam is recommended for those with halo nevi or a single halo nevus to make sure there are no atypical moles or malignant melanoma on the skin.
If you have a halo nevus and you have another mole that is changing, you need to be evaluated by your doctor immediately.
Oftentimes these types of moles go unnoticed, so it is recommended that you visit your dermatologist at least once per year for a full body examination. If there is a mole on your back you may not even be aware of it, so it’s always a good idea to get checked out.
Even if you are aware of a mole and are unsure if its appearance is changing over time, just go to your dermatologist to make sure. It’s always better to be overly cautious than to let a skin condition progress to a more dangerous level.