Eyebrow dandruff is typically caused by the same issues that cause dandruff on the scalp. In fact, nearly everyone who has eyebrow dandruff will also have scalp dandruff. Eyebrow dandruff can be more annoying though, because the bits of flaky white skin cannot be hidden under a hat or scarf and will sometimes fall into the eyes, causing irritation. Treating eyebrow dandruff is also similar to treating it on the scalp. Usually daily washing with a mild shampoo will help, although occasionally a medicated shampoo meant to treat dandruff is needed. In that case, care must be taken to avoid getting the shampoo in the eye.
Seborrheic dermatitis is itchy, oily, red skin that can appear anywhere on the body and is often the cause of those oily, white flakes. If your dandruff is caused by seborrheic dermatitis, the flakes will be large, yellowish in color and oily to the touch according to an article at Medline Plus. Daily washing with a gentle shampoo--rub a little on your eyebrows, too--will help treat this type of dandruff.
Simple Dry Skin
It's possible that your eyebrows are flaking because the skin under them is simply too dry. This is especially true if your eyebrows tend to flake in the winter months. In this case the flakes will usually be smaller and whiter, similar to flaking dry skin on any part of your body. Using an exfoliating facial wash followed by a moisturizer smoothed into your eyebrows will help if this is the case.
Malassezia is a yeast-like fungus that can cause dandruff, according to the physicians at MayoClinic.com. When the fungus has a growth spurt--usually for an unknown reason but sometimes because of excess oil on the skin--it eats the oil secreted by hair follicles, causing irritation, additional skin growth and then flaking.
The flaking from psoriasis sometimes affects the scalp and face, including the eyebrows, although physicians at MayoClinic.com report that it's rare to have psoriasis appear only on the scalp and eyebrows. If you have patches of psoriasis elsewhere on your body, it may also be the culprit in your eyebrow dandruff. If that's the case, your doctor should be able to prescribe medication to help stop the shedding of skin under or around your eyebrows.