The prophet (pbuh) commanded to ‘honour’ your hair, which has been understood to mean to take care of it especially by applying oil to it.
Jesus (as) is called Christ (from a Latin word that means anointed), which is also the meaning of the word Massiah (anointed in Arabic). He was given this name as he used to anoint himself with olive oil. In Islam the olive tree is a blessed tree and there is explicit command from the prophet (pbuh) to use olive oil to anoint our bodies and hair.
The hair itself is dead protein, and applying a thin layer of oil has been scientifically proven to protect the hair from protein loss and thus maintains the hair’s strength leading to less breakage. The oil also prevents excess drying that might also lead to the hair being damaged. Just imagine a glass of water with an oil layer over the water, will it evaporate?
Your hair and scalp is naturally slightly acidic and so is olive oil and thus it helps return your scalp’s and hair to it’s normal pH, this is helpful since shampoos (and most soaps) are alkaline. By maintaining your natural body’s pH you are helping more ‘good’ bacteria to grow and bad bacteria to die, leading to less infection to say the least. The pH imbalance also can lead to dandruff (caused by yeast). Btw anointing your hair does not mean oilining it until it’s dripping a trail behind you, literally a few drops massaged into it does the job.
Vinegar is used in Islamic medicine, and is one of the best way to get rid of dandruff (it is acidic) and works like a miracle to help with frizz and giving hair shine. Most people use it by adding a few tablespoons of vinegar to about a jug of water and using it to rinse thier hair between the shampooing and conditioning. The vinegar works as its acidity helps to flatter hair cuticles, reducing frizz, giving it shine and making it easier to detangle. While any vinegar type works many people like using apple cider vinegar. Btw, vinegar is water soluble and is easily washed away by water, and so you will never be left with it’s smell on your hair, and any left usually disappears after the hair dries.
Many people with experience and an interest in growing long hair suggest the use of natural silk to cover your pillow. This allows your hair to glide easily over the pillow as you move during the night. The friction caused with normal pillow covers leads to static electricity being created in your hair making it vulnerable to breakage. SubhanAllah the prophet (pbuh) suggested to the women of his household to cover their hair with natural silk. An easy way to maintain this sunnah without having to throw away all your old pillow cases and buying others is to buy a meter or so of pure silk and cut it to make small bandanas which you can wear during the day under your hijabs or at night before you go to sleep.
The prophet (pbuh) commanded his companions to comb their hair one day and miss the next. Remember that combing is traumatic to the hair so it’s good to give your scalp and hair a day’s rest. Also using the right type of comb does wonders, ages ago people used natural combs made from wood or horn, and they are much better than plastics. Plastics can lead to static electricity and as I said before this is not good for your hair. As it is not good for your wooden comb to get wet and not good for your hair to be combed wet (it is weaker and easier to break), it makes sense to comb your hair before you wash it or when it’s dry.
Your scalp absorbs anything you put on it, and this can be taken via the blood to your liver and other organs. Hence, it is wise for the sake of maintaining good health to use shampoos made from natural ingredients and those containing less harsh detergents.