Lactose Lactose is a natural sugar found in milk and milk products. It is sometimes extracted for use in other products.
Some people have difficulty digesting lactose ("lactose intolerance") because they have insufficient lactase, an enzyme naturally found in the digestive system. Wikipedia points out that about 75% of adults worldwide produce less latase in adulthood (more like 5%) for people of northern European ancestry.
There is, some, but not much research that indicates there may be a connection between alopecia and lactose intolerance. MedHelp suggests that people who have both lactose intolerance and alopecia could have celiac disease (gluten intolerance) as an underlying cause.
Talk to your dermatologist if you have severe hair loss and think you might be lactose intolerant. Taking latase orally when you consume milk products might help.