Differential Diagnosis for Red Greasy Patch on the Scalp
Single Most Likely Diagnosis
- Seborrheic Dermatitis: This condition is characterized by a red, greasy, and scaly patch, often found on the scalp, including the back of the neck. It's not typically itchy in its early stages, which aligns with the symptoms described.
Other Likely Diagnoses
- Dandruff: Similar to seborrheic dermatitis, dandruff can cause a red and greasy appearance on the scalp, though it's more associated with flaking.
- Oily Skin (Seborrhoea): Excessive oil production can lead to a greasy scalp, which might appear red due to irritation or inflammation.
- Folliculitis: Although it often presents with papules or pustules, a mild case could potentially appear as a red, greasy patch without distinct lesions.
Do Not Miss Diagnoses
- Tinea Capitis (Ringworm of the Scalp): Although it typically presents with itching, hair loss, and sometimes vesicles, a mild or early case might not have all these symptoms. It's crucial to consider due to its potential for significant hair loss and the need for antifungal treatment.
- Psoriasis: While psoriasis often presents with well-defined plaques and scaling, an early or mild case, especially on the scalp, might appear differently and could be mistaken for other conditions.
- Skin Cancer (e.g., Squamous Cell Carcinoma): Although less likely, any persistent skin lesion should be evaluated for the possibility of skin cancer, especially in sun-exposed areas or in individuals with risk factors.
Rare Diagnoses
- Keratosis Dessicata (Dry Scalp): Despite its name suggesting dryness, in some cases, it can appear greasy due to the body's overcompensation with oil production.
- Demodex Infestation: Demodex mites can lead to a condition that might present with a greasy scalp, among other symptoms, though this is less common.
- Hidradenitis Suppurativa (in rare cases affecting the scalp): This condition typically affects apocrine-gland-bearing areas but could, in rare cases, affect the scalp, leading to inflamed and potentially greasy-appearing lesions.