Hair starts out white and then gets its color from melanin, which also gives skin its complexion. According to Everyday Mysteries from the Library of Congress, the color and shade of your hair is determined by the blend of dark and light melanin, also called eumelanin and phaeomelanin, respectively. Hair color fades at about 10 percent to 20 percent every decade once you’re older than 30. Eventually it turns gray and then white. Environmental toxins and chemicals can give it a yellowish hue.

According to Pamela Ferrell, author of “Let’s Talk Hair,” yellow hair looks dirty and aged. The products you use to beautify your hair and get rid of that aged appearance could be making it worse. Because white hair has no color, it tends to pick up the color of the products you use. Also, chemical buildup from these products stains your hair, making it less white.

Styling tools such as curling irons, flat irons and hot combs can scorch your hair. It’s more likely if you use these tools repeatedly or at high temperatures. When white hair burns, it may become brown or yellowish. As Ferrell explains, once your hair is burned, there’s little you can do to reverse the discoloration.

Going too long between shampoos can also turn your hair yellow. Although shampooing is really to cleanse your scalp, your hair also gets washed during the process. Shampoo helps remove dirt, dust and pollution that your hair picks up from the environment. It also gets rid of residue from chemicals and perspiration.

Avoid using heat-styling tools on your hair. If you do use them, apply a heat-protective spray to your hair first and use them at low temperatures. Buy organic products that are less likely to leave sticky residue on your hair and shampoo your hair at least once a week. Whenever possible, buy products formulated for gray hair.

If you decide to color white or gray hair to combat yellowness, Ferrell recommends avoiding any product that contains phenylenediamine. Highlight the hair instead of applying full color. It gives your hair a warmer appearance instead of a stark, unnatural look. If coloring is not your style, give your hair a trim and avoid the factors that cause yellowing as your hair grows back.