Two of the leading causes of sudden hair loss are genes and stress. Hairloss may be inherited, but this is usually not sudden, but happens over time. What is sudden about it is that you notice large clumps of hair staying on the brush or comb when you do your hair each morning. Although this is common in males, it does happen to females as well. Severe stress has also been identified as a cause of sudden hair loss because it interferes with the inner workings of the body