There are many reasons for a scaling scalp including underlying medical conditions like psoriasis, or fungal infections. In older patients who have lost some of their natural sun protection (hair), precancerous lesions can feel scaly in the scalp as well.
Plaque psoriasis can cause scaling patches of skin in the scalp, just as it causes these patches on the elbows and knees. The skin in the scalp will be inflamed with thick, silvery scale that causes it to itch and occasionally be tender.
Fungal infections on the scalp, or tinea capitis (commonly known as ring worm) is most frequently found in children. Risk factors include humid climates and contact with pets.
Seborrheic Dermatitis is a very common rash affecting the scalp from a hypersensitivity reaction to yeast. This is the most common cause of dandruff.
Pre-cancers (actinic keratoses) from significant sun exposure,can lead to scaly patches on the scalp. Pre-cancers (actinic keratoses) typically present as scaling lesions that do not go away on their own and need to be evaluated.
Irritant contact dermatitis from fragrances and preservatives in personal care products can cause irritation of the scalp leading to redness and scaling.
Scaling of the scalp can be minimal with light scaling throughout the scalp and only mild associated itching, or more severe, with thick and greasy scale that coats the hairs. In the case of fungal infections, the lymph nodes in the neck can become inflamed and be felt through the skin, sometimes with tenderness on palpation. Rarely, scaling scalp can be associated with hair loss.
Because scaling scalp is a common problem, most dermatologist can make a diagnosis after evaluating the scale and the skin on the scalp. If there is more than one likely explanation for the scaling, testing can be done to determine the diagnosis, including a swab of the scale for a fungal culture, or a biopsy (sample) of the skin for microscopic evaluation by a pathologist.