According to Derma Doctor, eyebrow loss may be caused by one of many factors, including endocrine imbalance, chemotherapy, infiltrating cancer, inflammation, mineral poisoning, skin growths, infection and certain medications. While diminished eyebrow growth can be the result of excessive eyebrow plucking, full-scale hair loss of the eyebrows generally points to another underlying cause.
Derma Doctor explains that an imbalance in the thyroid hormone, which is not unusual with various endocrine disorders, is a common cause for severe eyebrow loss. About.com notes that eyebrow loss is one of the most common signs of hyperthyroidism and tends to occur in an unusual pattern toward the edge of the eyebrows.
Infections and other conditions of the skin that agitate or block the subdermal hair follicles may also play a role in eyebrow loss or prevent the hairs from growing at all. According to Derma Doctor, medical treatments, such as chemotherapy, and other types of prescription drug treatments may result in hair loss that is either specific to the eyebrows or that affects hair growth on the entire body. Even common over-the-counter nonsteroidal anti-inflammatory medications used for pain relief, such as naproxen, ibuprofen and acetaminophen, can lead to an allergic reaction that causes eyebrow loss.