https://www.medicalnewstoday.com/articles/313968#causes
What causes lumps behind the ear?
Causes
When to see a doctor
Tests and diagnosis
Lumps behind the ear can have many possible causes, including problems in the skin or bone.
Swollen lymph nodes, infections, and certain cancers can also lead to lumps.
Most cases of a lump behind the ear do not present a cause for concern, however, and normally resolve without treatment.
Causes
There is a range of skin conditions and infections that can cause lumps behind the ear.
Lumps in the skin
There are many possible causes of lumps behind the ear.
The three main noncancerous causes of lumps behind the ear are:
acne
skin cysts
lipomas
Acne lumps behind the ear
Acne is a common skin condition that might cause a lump behind the ear.
In acne, pores in the skin become blocked with sebum. Sebum is an oily substance secreted by units at the base of hair follicles.
The sebum mixes with dead skin cells and can form a layer called a comedone.
A pimple might then become infected and inflamed if certain bacteria enter the comedone.
Inflamed pimples can grow and, in their most severe form, form lumps called acne cysts.
If acne is causing the lump, it may cause pain when pressed. Other cysts and pimples on the head are likely to accompany pimples or cysts behind the ear, especially on the face.
Cystic acne is an unpleasant condition that can lead to scarring. Doctors can help manage cystic acne with effective treatments, however.
Cysts behind the ear
A cyst can occur anywhere in the skin, including behind the ear.
Skin cysts are fluid-filled sacs. They form a raised, dome-shaped area on the skin. Sometimes, they have a black spot called a punctum at the top.
They can move around freely and are not fixed in place. A doctor should examine any skin lump that cannot be moved from side to side.
Cysts in the scalp tend to be pilar skin cysts. In this type, the lining of the sac is made of hair root cells.
Sebaceous cysts can also occur. These form on the glandsTrusted Source responsible for the oily substance that moisturizes the skin and hair.
Other cysts are made of cells from the surface of the skin, known as epidermoid cysts. Finally, there are also sebaceous cysts, which are less common and contain an oily substance.
Lipoma
Lipoma is another possible cause of lumps behind the ear. Lipomas are harmless, fatty lumps. They are not cancerous, grow very slowly, and do not spread.
They are more common on other parts of the body but can occur anywhere under the skin, including behind the ear.
A lipoma feels soft to the touch. They are not usually tender or painful unless they press on nearby nerves.
They will usually occur in a limited number of places. In rare cases, some people have many lipomas at once.
These lumps are often small and range from the size of a pea to inches across.
Cosmetic surgeons can remove unsightly lipomas, but it is safe not to receive treatment. If necessary, a surgeon can remove a lipoma.
Cysts and lipomas are similar types of lump. A lipoma sits deeper in the skin than a cyst, as well as feeling softer.