Itchy scalp due to dandruff can have many causes. For example, how often you wash your hair can lead to the condition. Infrequent washing can cause a buildup of oil and skin cells and lead to dandruff flakes. Hair that's washed too often, on the other hand, can also lead to itchy scalp, because the oil that protects the scalp gets stripped away. Cold weather and the dry indoor air can also lead to a dry scalp [source: Mayo Clinic]. Stress can affect dandruff, too. For instance, it can cause conditions like seborrheic dermatitis, which is characterized by an oily, waxy scalp and white or yellowish-brown flakes, to flare up [source: American Academy of Dermatology].
One major contributor to itchy scalp is the skin condition called psoriasis. Caused by a malfunction in the body's immune system where overactive white blood cells mistakenly heal healthy skin cells, psoriasis can lead to a buildup of itchy, red, swollen patches on the body. The malfunction may have its roots in both genes and the environment [source: Mayo Clinic].
Unlike lice and despite its name, scalp ringworm is not caused by a small pest. It's a mold-like fungal infection and related to athlete's foot and jock itch. The name comes from its resulting round patches of baldness or scaliness [source: Mayo Clinic]. Another fungus, a yeast-like one known malassezia, can cause dandruff. Many people have this fungus but experience no problems. For others, some additional factors, including an oily scalp, stress, hormones or illness, may play a part in turning the fungus from a benign presence to an issue. For example, people with Parkinson's disease or those recovering from a heart attack or stroke are more susceptible to dandruff [source: Mayo Clinic].
Sometimes an itchy scalp will heal over time -- an infant's cradle cap or a sunburned scalp, for example, tend to go away after a while. Some itchy scalp conditions can be resolved easily with a simple change of daily habits. Other problems require medical intervention. Read on to find out when you should see a doctor.