A bump on the skull can be a surprising and sometimes concerning discovery. Most bumps are harmless, representing common physical variations or minor issues involving the layers that cover the skull bone. The head is composed of several distinct tissue layers—skin, subcutaneous fat, muscle, and the periosteum—all resting on the hard, protective cranial bone. A bump can originate from any of these layers, which is why they vary widely in texture, mobility, and cause.
Normal Anatomical Variations
Many perceived lumps on the head are not growths at all, but rather naturally occurring features of the skull’s bony structure. These features are generally fixed, present since development, and often symmetrical or located along the midline of the bone.
The most commonly felt bone protrusion is the External Occipital Protuberance (EOP), a bump located centrally at the back of the head where the neck muscles and ligaments attach. This feature can vary significantly among individuals, sometimes becoming quite pronounced, a variant known as an occipital spur or bun. It is not a medical concern unless it causes localized tenderness when lying down.
Another variation is the Sagittal Keel, which appears as a slight ridge running along the top of the skull’s midline. This feature is a non-pathological variation where the two parietal bones meet at the sagittal suture. While rare in modern humans, it is usually more prominent in adult men.
The bony ridges above the eye sockets, known as the supraorbital ridges, are also subject to natural variation. The prominence of these ridges varies, often being more noticeable in males due to hormonal influences during development. These fixed protrusions are part of the frontal bone’s architecture.
Bumps Caused by Injury or Inflammation
Bumps that appear suddenly often result from either recent trauma or a localized inflammatory response. Acute blunt force trauma frequently causes a hematoma, commonly referred to as a “goose egg,” which is a collection of blood under the skin. A subgaleal hematoma occurs when blood pools in the space above the periosteum, the membrane covering the skull bone.
Small, superficial hematomas can take a few weeks to resolve as the body reabsorbs the pooled blood. After a more severe injury, a secondary bump may form months or even years later, representing a bone callus. This hard, permanent lump is the body’s natural response to healing a fracture, where new bone tissue overgrows the site of the break.
The remodeling process of a bone callus can take months to years, sometimes leaving a small, thickened area of bone. Superficial inflammatory bumps may also be caused by an infected hair follicle or folliculitis, which can feel like a firm nodule under the scalp. These are typically tender, red, and warm to the touch, distinguishing them from bony or fatty masses.
Common Benign Growths and Cysts
A variety of slow-growing, benign masses can develop in the soft tissue or bone of the skull. Lipomas are among the most frequent benign soft tissue tumors, composed entirely of mature fat cells. These masses are typically soft, rubbery to the touch, and easily movable when gently pressed beneath the skin. They can occur anywhere on the scalp or forehead.
Epidermoid cysts are sacs filled with keratin and skin debris. When located in the scalp, they usually feel smooth, dome-shaped, and relatively mobile, sometimes slowly increasing in size over many years. The skin overlying the cyst often appears normal unless the cyst becomes inflamed or ruptures.
Osteomas are slow-growing, benign tumors made of mature bone tissue. These masses are almost exclusively found in the craniofacial region, often on the outer surface of the skull or within the sinuses. Because they are made of bone, they are characteristically hard and completely fixed to the underlying skull. While usually asymptomatic, large osteomas can cause issues if they compress nearby nerves or block sinus drainage.
When to Seek Professional Medical Advice
While most skull bumps are harmless, certain characteristics warrant a medical consultation. Seek a healthcare provider if a bump appears suddenly following a significant head trauma, particularly if accompanied by confusion, memory loss, or persistent vomiting.
A physician should evaluate any bump that rapidly changes in size or shape, or one that is fixed and has recently appeared without a known injury. Signs of infection, such as increasing pain, warmth, redness, or pus drainage, also require professional attention. Any skull bump associated with neurological symptoms, including dizziness, vision changes, slurred speech, or a worsening headache, requires immediate medical assessment.