A variety of conditions can lead to the development of pus on the scalp. One of the most common causes is folliculitis, where bacteria builds up in the hair follicles on the scalp, leading to infections that can range from mild, acne-like spots to deep, painful boils. Pus frequently develops in cases of ringworm, a fungal infection of the scalp that often affects children. It can also be the result of a condition called dissecting cellulitis, where large, non-infected pustules form under the skin of the scalp, damaging the follicles and typically causing hair loss.
Pus on the scalp is often caused by folliculitis. This condition, which is basically a bacterial infection of the follicles, can occur in a number of ways, including damage to the follicles from excessive pulling or irritation, buildup of perspiration on the scalp, or overexposure to hot or humid environments like saunas or hot tubs. For some people, the infections are mild and only affect the upper layers of skin, causing small, white pustules that resemble pimples. Others may develop more severe, deeper infections that can turn into hard, painful boils which require medical attention to prevent follicle destruction and scarring.
Another issue that often leads to pus on the scalp is ringworm, also known as tinea capitis. Ringworm is a highly contagious fungal infection that commonly occurs in children. It initially causes a flaking, itchy rash, but as the disease progresses, affected people may also have an allergic reaction to the fungus that causes swollen, pus-filled blisters to form in the area. These lesions may ooze and become infected, and if left untreated may eventually cause scarring and hair loss. Ringworm can often be successfully treated early on without a doctor's intervention using good hygiene and over-the-counter antifungal medications, but cases that do not clear easily or show signs of more severe infection often require prescription medication.
Patients with dissecting cellulitis also usually form pus on the scalp. One of the main symptoms of this condition is the formation of pustules under the skin over large areas of the scalp. These initial pockets of pus are typically not due to infection and do not contain bacteria. Over time, however, the condition can damage or destroy the follicles and a secondary bacterial infection may occur. This condition often leads to significant scarring and baldness on large portions of the scalp.