Scalp inflammation is the body’s protective response to irritation or injury affecting the skin of the head. It can manifest as redness, itching, tenderness, or flaking, indicating an underlying issue. Many factors can trigger this response, from common skin conditions to various infections. It is a symptom of an underlying process, not a standalone disease.
Common Skin Conditions
Seborrheic dermatitis
Seborrheic dermatitis is a common inflammatory skin condition often affecting areas rich in oil-producing glands, including the scalp. It results in red skin covered with greasy, yellowish scales and can cause itching. An overgrowth of Malassezia yeast, a naturally occurring skin microbe, is associated with its development. The yeast contributes to the inflammatory response, leading to characteristic flaking and discomfort on the scalp.
Psoriasis
Psoriasis is a chronic inflammatory condition where skin cells multiply faster than usual, accumulating on the surface. On the scalp, this rapid turnover leads to thick, silvery-white scales over red patches. These psoriatic plaques can be itchy or sore, and scratching can lead to temporary hair loss. The condition is an autoimmune disorder, meaning the body’s immune system mistakenly attacks healthy skin cells.
Contact dermatitis
Contact dermatitis on the scalp occurs when the skin reacts to a substance it has touched. This reaction can be categorized into two main types: irritant contact dermatitis or allergic contact dermatitis. Irritant contact dermatitis happens when a substance directly damages the skin, while allergic contact dermatitis is an immune system reaction to an allergen. Both types can cause redness, itching, and blistering on the scalp.
Infections
Fungal infections
Fungal infections, such as tinea capitis (ringworm of the scalp), can cause inflammation. These infections are characterized by itchy, scaly, and red patches on the scalp, often with hair loss. The fungi, typically dermatophytes, infect the hair shafts and follicles, leading to inflammation and sometimes broken hairs. Tinea capitis is contagious and can spread through direct contact or shared items.
Bacterial infections
Bacterial infections can also lead to scalp inflammation, often presenting as folliculitis. This condition involves infected hair follicles, resulting in small, red, pus-filled bumps that can be itchy, tender, or painful. Staphylococcus aureus is a common bacterium responsible for these infections, entering follicles through minor skin breaks or irritation. Without proper care, these localized infections can spread or recur.
Viral infections
While less common than fungal or bacterial causes, certain viral infections can contribute to scalp inflammation. For example, shingles, caused by the varicella-zoster virus, can affect the scalp, leading to painful rashes and inflammation if nerve pathways supplying the scalp are involved. These viral presentations are often distinct from typical bacterial or fungal infections in their appearance and progression.
Reactions to Irritants or Allergens
Hair products
Many hair products contain ingredients that can trigger an inflammatory reaction on the scalp. Shampoos, conditioners, hair dyes, styling products, and perms may contain fragrances, preservatives, or harsh chemicals like paraphenylenediamine (PPD). Exposure to these substances can lead to contact dermatitis, causing symptoms such as redness, itching, burning, and flaking. Identifying and avoiding the offending product is the main approach to managing such reactions.
Environmental factors
Environmental factors can also contribute to scalp inflammation. Exposure to harsh weather conditions, such as extreme cold, dry air, or intense sun, can irritate the scalp’s skin barrier. Pollution, including particulate matter and airborne chemicals, can settle on the scalp and provoke an inflammatory response in sensitive individuals. Certain plant exposures, like poison ivy or oak, if they contact the scalp, can also induce an allergic reaction.
Mechanical irritation
Mechanical irritation of the scalp can also lead to inflammation. Habits like excessive scratching can break the skin barrier and introduce bacteria, leading to further inflammation or infection. Similarly, tight hairstyles, such as braids or ponytails that pull on hair follicles, can cause traction folliculitis. Rough brushing or vigorous towel-drying can also damage the scalp, initiating inflammation.
Autoimmune and Rarer Conditions
Lupus erythematosus
Lupus erythematosus is a systemic autoimmune disease where the immune system attacks healthy tissues throughout the body, including the scalp. When it affects the scalp, it can cause inflamed, red patches that can lead to scarring and permanent hair loss, known as discoid lupus erythematosus. The inflammation results from the body’s own immune cells targeting the skin and hair follicles. This condition requires careful medical management to control the immune response.
Lichen planopilaris
Lichen planopilaris is a less common inflammatory condition that specifically targets hair follicles on the scalp. This autoimmune-related disorder leads to redness, scaling, and itching around the hair follicles. Over time, the inflammation can destroy hair follicles, resulting in permanent, patchy hair loss and scarring. The affected areas often appear smooth and shiny due to the absence of hair and scar tissue.
Other rare systemic conditions
Other rare systemic conditions can also cause scalp inflammation. These include certain forms of alopecia, such as dissecting cellulitis of the scalp, which presents as painful nodules and abscesses that can lead to scarring alopecia. Some less common inflammatory dermatoses or underlying systemic illnesses may also manifest with scalp inflammation, often requiring specialized diagnostic approaches to identify the root cause.