Seborrheic dermatitis — patches of scaly, irritated skin
Seborrheic dermatitis is a common skin condition in the general population, but even more commonly found in people with PD. It causes patches of scaly, red skin and dandruff, primarily on the scalp and on the oily parts of the face such as the sides of the nose. In PD, it is thought to be caused by over-secretion of oils from the sebaceous glands in the skin. In much the same way that dysfunction of the autonomic nervous system (the nerves that control automatic body functions) cause non-motor symptoms in PD such as blood pressure dysregulation and urinary abnormalities, autonomic dysfunction of the nerves that control the oil glands of the face can cause seborrheic dermatitis.
A study demonstrated that seborrheic dermatitis in the general population was associated with a small increased risk of developing PD and may precede diagnosis, much in the same way that smell loss, REM behavior sleep disorder and constipation may precede PD diagnosis. Of course this does not mean that everyone with seborrheic dermatitis will go on to develop PD but it suggests that in some people, the nerve damage that leads to seborrheic dermatitis is a harbinger of PD.
Seborrheic dermatitis usually can be controlled with lifestyle changes or topical creams. Wash your skin regularly and avoid harsh soaps and products that contain alcohol. If the condition does not clear up, an over-the-counter mild corticosteroid cream may help. If simple changes are not effective, then consult with a dermatologist who may want you to try a prescription cream.