Does Trimming Hair Help it Grow?

The idea that trimming hair will make it grow faster is a fairly common belief. But this widespread misperception has no basis in physiology, because hair of a given type grows at the same rate, regardless of its length. A number of factors can make trimmed hair appear to grow in faster or thicker than hair that is left untrimmed. Exploring these factors and understanding how hair grows may give you a better appreciation for your own hair and its natural growth process.

Hair Fibers

Trimmed hair may seem to grow more quickly because hair fibers do not have a uniform shape and thickness along their entire length. A new hair has a thin, tapered tip when it emerges through a pore in the skin. Over time, the keratin protein cells that form the hair fiber build up, and the hair grows longer and thicker. When we cut a hair, we remove the tapered tip, leaving the thickest part of the hair as its new tip. Even though cut hair grows at the same rate, it may seem thicker and healthier because of the absence of tapered ends.

Comparative Growth

Hair growth is often noticeable and dramatic in someone with short hair, while a person with long hair may appear to have a much slower growth rate. In reality, their hair probably grows an average of a half-inch per month, just like most people's. Despite this fact, a person with a crew cut could double his hair length in just a month or two, while a woman with long hair may not appear to need a trim for several months. The contrast is especially striking when someone with long hair switches to a much shorter style and discovers that she now needs to visit the stylist much more frequently to maintain her new look.

Hair Structure

In addition to being made up of keratin proteins, every strand of hair contains three layers. The thin, exterior layer is the cuticle, which is colorless and protects the hair fiber. The cortex, which lies within the cuticle, is thicker and determines whether hair is curly or straight. It also contains melanin, which gives hair its color. The inner layer of the hair is the medulla, whose reflective properties give hair its shine and tone. Hair fibers are rooted in follicles within the skin and strengthened by sebaceous glands, which secrete oil to provide moisture.

Phases

There are three phases of hair growth. During anagen, hair grows actively for anywhere from two to eight years. How long anagen lasts determines the maximum length of a person's hair, which can range from just over 1 foot to more than 4 feet. After anagen, the hair follicle shrinks and fades during a transitional catagen phase of two to four weeks. Telogen, the final phase, lasts two to four months while the hair lies dormant, but stays attached to the follicle. After telogen, anagen begins again, and new growth pushes out the existing hair. The average person naturally loses 50 to 100 hairs per day because of this process, usually while showering or brushing hair.

Encouraging Growth

Do-it-yourself techniques and commercial products and services to encourage hair growth abound, but it can be hard to separate fact from fiction. In general, it pays to maintain good overall health through a balanced diet and exercise, and to take care of your hair through a consistent hygiene and grooming routine. A scalp massage like the kind experienced when thoroughly washing your hair is one of the few proven ways to promote healthy hair growth. Massaging the scalp can stimulate the follicles and encourage blood flow. For any treatment that is more exotic or invasive, do careful research and consult a trusted hairstylist, pharmacist or doctor.

References

• Basics of Hair Growth
• Naked Science Forum