These may be upsetting, but they usually are not caused by serious medical problems. Hair loss, including thinning and breaking, is the most common scalp problem. Most people lose from 50 to 100 hairs per day. Some possible causes for severe hair loss are: damage to the hair from hair care products, (dyes and permanents, curling irons, or hair dryers), recent surgery, high fever, or emotional stress, or poor nutrition (especially lack of protein or iron in the diet).