What Are Hot Roots?

‘Hot roots‘ is a general term to describe hair in the scalp area that’s lighter than the full length of the hair to the ends. You don’t have to be a trained hair professional to learn how to avoid hot roots when coloring hair, but it’s important to understand why they occur.

With a couple of exceptions (natural redheads and people whose hair is turning gray), most hair is naturally darker when it grows out from the scalp. As it continues to grow out and get longer, hair is not only aging (compared to new hair growing in), but it’s also exposed to environmental elements and natural sunlight. As a result, hair tends to get lighter toward the ends.

Why Do Hot Roots Happen?

There’s no shortage of explanations on how to avoid hot roots, and, likewise, there are plenty of ideas about why they happen in the first place. Here are the two most popular theories:

Theory #1: Body Heat

The human body emits heat; its normal temperature is 98.6 degrees Fahrenheit or 37 degrees Celsius. The scalp also generates body heat, and therefore, the hair growing out from it is “hotter” than the hair located throughout the length of the strands to the ends, which are further away.

Regardless of its source, heat accelerates the speed of the coloring process. When you apply dye or bleach to your hair, the scalp heat combined with the heat generated by the chemical reaction can make the hair that’s closest to your scalp lighter than the rest of your hair. Think of it like throwing kerosene on a barbecue grill.

Theory #2: Keratinization

Congratulations! You can finally say that something you learned in high school biology applies to real life. Remember when you and your lab partner looked at a strand of hair under a microscope? It was probably then that you learned for the first time that hair and fingernails are made up of dead cells. The process of accumulating these dead cells (keratin) that eventually form into hair strands is called “keratinization.”