To be clear, dandruff, true dandruff, is not a disease, nor is it a symptom of disease. It is part of the natural human condition to shed the outermost layer of skin. Dandruff is an indication that new skin is rising from underneath. That old skin has to go somewhere, of course, which generally happens when we sleep, are in the shower and go about our daily lives. (In case you didn’t know this, most household dust indirectly originates from human skin. Dust is the dead carcasses and feces of tiny house-dust mites -- Dermatophagoides farinae and related species -- which eat our skin before they depart this life and land on our coffee tables and computer screens.) But it’s true that some people get more dandruff than others. And depending on the nature and relative cleanliness of the hair in your scalp, the natural sloughing off of dead scalp skin might accumulate in your hair. In the majority of cases, the fix is to shampoo more often, perhaps with a pyrithione zinc-based shampoo, the active ingredient in most over-the-counter dandruff shampoos. There are also other causes of itchy, flakey skin on the scalp. Some are downright frightening, and in advanced cases the irritation can lead to spot hair loss, aka alopecia areata. The following conditions may lead to an itchy flaking on the scalp:
Generally considered a sensitivity to hair care products, this skin inflammation, which resembles a burn, is a reaction to an irritant or allergen. Other symptoms include itching, tenderness, swelling and skin lesions (rash, vesicles and bullae/blisters).
Itchy skin that can occur anywhere on the body, including the scalp, eczema produces skin that becomes scaly, dry and thickened from scratching. Ultimately, the skin oozes fluid and crusts over. It tends to run in families, coincides often with allergies and asthma and is believed to be an over-response of the immune system to soaps and detergents, heat or cold and contact with pet dander. It is not contagious.
Inflamed follicles (folliculitis)
The follicles, the source of each strand of hair, can become inflamed from infection by a fungus or staphylococcus bacteria. This infection is often a secondary effect of eczema or dermatitis. Other causes of folliculitis might include diabetes, tight clothing (including hats and ball caps), poor hygiene in combination with heat and humidity, and use of hot tubs.
More commonly found elsewhere on the body (elbows and knees), psoriasis can be found on the scalp and is often mistaken for seborrheic dermatitis. It is seen as thick, silvery scales.
Characterized by flakey white or yellow scales originating on red, greasy skin on the scalp, it is largely found on the scalp. Seborrheic dermatitis also appears on the body where oil glands are plentiful (eyebrows, sides of the nose, the groin area and armpits). It may be a result of irritation from Malassezia, a yeast, and can be stimulated by stress, oily skin, fatigue, extreme weather, poor hygiene and use of personal care products containing alcohol. Obesity also can be a risk factor, as can HIV infection. It more often is seen in men than women. Chronic itching and scratching can lead to temporary, spot hair loss and secondary fungal infections. From a preventive standpoint, three things seem consistent across all conditions: Pay attention to the symptoms, particularly if other members of your family have similar symptoms and diagnosed conditions. Maintain proper hygiene by shampooing frequently. And if symptoms persist over several weeks after trying mild, over-the-counter remedies, go see your doctor.