The number of times you dye your hair without damaging it too much depends on several factors. If your hair is healthy, you can dye your hair every six to eight weeks. If you heat-style or heat-relax your hair, you need to deep-condition your locks. The U.S. Food and Drug Administration says follow hair-dye package directions carefully and do a patch test before colouring your hair.
Your Hair Condition
Check the condition of your hair by brushing it with a large round brush. What does your hair look like in the mirror? Does it look healthy or dry and dull? If your hair is very fine or brittle, colour your hair just once or twice per year.
You can also use deep conditioners once a week. Available at chemists or beauty-supply stores, deep conditioners are loaded with more moisturising ingredients than standard conditioning products.
Test for Strength
Testing hair strength can give you an indication of whether your hair is healthy enough to be chemically treated. Perming or colouring weak hair can cause hair loss and breakage.
To test hair, pluck out a single strand from both sides of your head. Hold one hair between your thumb and index finger. Use your other hand to run along the hair very quickly. This should create curls and kinks. Now stretch the curly hair, pulling it as tight as you can and then let go. If your hair goes back into its original straight shape, then your hair is strong and healthy. However, if your hair breaks or becomes even more curly, you have weak hair.
Inspect the ends of your hair. They should be straight with only a few split ends. To keep hair split-end free, get regular trims.
Nutrients You Need
Lack of vitamins may cause your hair to thin and look dull. For healthier hair, follow good nutrition and take some vitamins. Biotin, or vitamin H, produces keratin that prevents greying and hair loss. It is found in foods such as poultry, whole grains, egg yolks and nuts. Other vital nutrients for your hair are foods rich in omega-3 fatty acids. Salmon and ground flaxseed, packed with these healthy fats, help improve scalp health.
You can also take wholefood multivitamins, which are made from food products instead of chemicals, and mineral supplements. All are available at health food stores.
If you're pregnant, consult your doctor before dying your hair. Mayo Clinic obstetrician Dr. Roger Harms says a small amount of dye should not harm a developing foetus. But because there are not enough studies on this subject, some doctors recommend postponing hair colouring during the first trimester as a precaution.