Flat irons are an essential beauty tool for a smooth, straight style, but over time, they can damage your hair and cause split ends. Hair has strength, but when the center, or cuticle, of a hair is damaged from direct heat, the hair tip splits, causing frizziness.

The American Academy of Dermatology notes that hair growth takes place inside the hair follicle. The hair follicle is located within the epidermis layer of skin. The hair shaft, which is porous, grows inside the follicle and will become soft when wet.

Essential oils contain high concentrations of the chemicals that give plants their essence -- or fragrance and flavor. Distilled from the leaves, bark, flowers and other parts of plants, these oils have been used for centuries to promote hair growth in Chinese and Ayurvedic medicine.

It seems like most people aren’t happy with their natural hair. If you have curly hair, you might long for straight, while a person with curly locks longs for your straight tresses. Hair color is another treatment that is increasingly popular, whether you are fighting grays or simply want a new look.

Hair growth in men and women is governed by hormones called androgens. Specifically, androgens are the hormones that cause the development of "masculine" features, both in men and women. One of the characteristics that androgens are able to affect are hair follicles.

Nails and hair are both made from keratin, and any changes in your body’s keratin production will impact their health. For example, healthy hair and nails should have a certain amount of flexibility. Dehydration or any form of malnutrition can cause your nails and hair to become brittle and easily broken.

Anyone who lives in a humid climate can tell you that a rise in humidity often means a rise in the amount of frizz in their hair.

Everyone's hair contains keratin proteins, but people with curly hair have less keratin. Keratin treatments seal this protein into the hair, leaving it sleeker, straighter and easier to style. While this many sound like a dream, the rules surrounding a keratin treatment are a bit stringent.

Restoring the pH of the scalp may help prevent hair loss from dandruff, bacteria or fungus. Every liquid substance on Earth has a pH, or an acid-base, measurement. Very few substances are neutral; most are either acidic, such as vinegar, or basic, such as bleach.

Brylcreem is a brand of hair care products that originated in England in the late 1920s with a canned pomade that gave hair hold and shine, notes the "Encyclopedia of Hair: A Cultural History" by Victoria Sherrow, and was the first hair product marketed exclusively to men.

Several commercial over-the-counter shampoo products contain active ingredients designed to target and alleviate dandruff. The main active ingredients used include salicylic acid, zinc pyrithione, coal tar, resorcine, selenium and ketoconazole, according to the National Institutes of Health.

Fine hair takes an extra fine level of care -- it can easily be damaged by the elements and weighed down by the buildup of harsh chemicals in hair products. Fine tresses that are dry and brittle, flat or frequently frizzy should be treated with deep conditioners that will nourish and revitalize the hair.