Finding a lump on your neck, behind your ear, or on your back can be a startling experience. It often happens when you’re brushing your hair, washing up in the shower, or simply checking your reflection in the mirror—and suddenly, there it is, a bump you hadn’t noticed before. For many, the first reaction is panic: Is it cancer? Is it serious? While it’s natural to worry, the reality is that most lumps under the skin are harmless. Still, it’s important to understand what they could be, why they appear, and when a medical evaluation is necessary.
One of the most common causes of such lumps is an epidermoid cyst. These are non-cancerous growths that form just beneath the skin and often develop slowly over time. Epidermoid cysts are most frequently seen on the neck, back, face, or behind the ears. They occur when skin cells that are meant to shed naturally become trapped beneath the skin’s surface, forming a small sac filled with keratin, the same protein that makes up your hair and nails.
In most cases, epidermoid cysts are painless and remain stable for months or even years. However, complications can arise if the cyst becomes irritated or infected. Signs of infection include redness, warmth, swelling, tenderness, and sometimes fluid leakage with a noticeable odor. Certain factors can increase the risk of developing cysts, such as having acne-prone skin, experiencing minor skin injuries, blocked pores, or, in rare cases, inheriting genetic conditions like Gardner syndrome. They are also more commonly seen in adults, particularly men.
Keep reading — what comes next could help you recognize warning signs…