Brows help define and shape your face. They are, as brow specialist Joey Healey once told me on my podcast, Clean Beauty School, a foundation element. “I believe in the foundations of beauty, which are skin, hair, teeth, and brows,” he says. “If you focus on the basics, you can build a routine out from there.” 

Within the beauty space, they also occupy a unique category: Part hair care, part skin care, and part makeup. In order to truly take care of the fine little hairs, you need to ensure each step isn’t jeopardizing the intercity of the hair fiber or follicle. Don’t worry—we’ll spend adequate time going over the steps later. 

Brow hairs are like all other hairs on the body in that they are made up of the protein keratin. Keratin, and all proteins, are made up of amino acids (called the building block of proteins). The keratin found in hair is made up of the amino acids cystine, glutamic acid, glycine, leucine, and arginine, and more. 

The hair strand has three parts: the cortex, medulla, and cuticle. For the purposes of hair care, we typically focus on the cuticle, which is the outermost layer. If you look at it closely (as in with a microscope), it resembles a roof: overlapping shingles that act as a protective layer, while allowing for some absorption. 

Brow hair follicles (or what the hair grows out of in the skin) look identical to the hair follicles on the rest of the body. What’s different, however, is their growth cycle. Board-certified hair restoration surgeon William Yates, M.D., notes that “eyebrows have a three- to four-month growth cycle.” This is why brow hairs are shorter than the hairs on your head, for example.