Hair dyes can trigger minor to severe allergic reactions in a small percentage of users. They can also cause dry, brittle hair and hair breakage with extended and frequent use. According to the American Cancer Society, the evidence linking personal hair dye use and cancer is limited and conflicting. As of 2014, personal use of semi-permanent and permanent hair dyes is not considered a known risk factor for cancer.Know More
Professional hairstylists may have cause for concern, however. According to the American Cancer Society, numerous studies have suggested that workplace exposure to hair-dye chemicals can lead to a slightly elevated risk of bladder cancer. These findings have led the International Agency for Research on Cancer to identify occupational exposure to hair dyes as a probable risk factor for cancer.
Another potentially serious but rare side effect is an allergic reaction to the chemical paraphenylenediamine, a common ingredient in commercial hair dyes. This allergy affects about one in 250,000 people, and those with a history of allergies should be especially cautious of using a chemical dye. An allergic reaction to hair dyes may present itself as an itchy, red rash around the face and neck, and less commonly a rash on the scalp and extreme swelling of the face. The allergy can become more severe over time, resulting in blisters, hives and difficulty breathing, and continued use can be fatal.Learn more in Hair Color
Hair should be neither too clean nor too dirty before being dyed, so Allure magazine recommends washing it eight to twelve hours before dyeing to get the truest color. Hair that is squeaky clean or exceptionally oily or dirty can interfere with the coloring process when dye is applied.Full Answer >
Most hair coloring experts advise waiting a few weeks between dye applications, because newly colored hair needs time to dry and air out. The length of time between hair dyes varies for each person, however.Full Answer >
It is possible to highlight hair that has already been dyed, but it's better to highlight using foils. Sometimes, at-home kits make hair appear brassy or not the color that was planned, so it's important to recognize the risks involved before doing it personally.Full Answer >
Hair bleach is damaging to the hair and should only be applied by a professional. Bleaching hair can permanently raise the hair cuticle, which may contribute to a rapid loss of moisture.Full Answer >