Unlike temporary hair dye, which washes out after 8 or so showers, permanent hair colour does not wash out.
It covers greys permanently, and can be used to lighten, darken, or change the tone of your hair.
Sometimes you can go to a hairdresser to dye your roots, but that often isn’t an option (either because you are too busy, you are stuck at home, or you prefer a more affordable alternative).
Roots generally become clearly visible after four weeks. And by six weeks, they are about two centimetres long and craving an update.
So sometimes, making this fine-tuned regular home ritual can be a great approach.
Use a comb with a tail to part your hair from front to back at roughly one centimetre intervals.
Apply the colour at the roots first. They dye quicker, and are the parts that need updating, so you’ll want to go slowly and do a thorough job.
Wait twenty minutes, then, massage the dye around and apply the remaining dye to the rest of your hair to freshen up its colour and provide full coverage.
Wait another five minutes or so, then rinse the hair dye out.
If you need to bleach your hair before dying the roots, do that of course, but only bleach the roots.
Be sure to use lots of conditioner, to help repair or prevent any damage from the bleach.
Obviously, the colour that looks best will depend on your individual appearance and your own personal preferences.
Choose a colour that is just a little darker than what you want, to allow for a bit of fading.
A black dye next to older and paler skin can be quite harsh, but it can also work if you love black.
Warm colours work well with warm skin tones such as pink and olive, while cool and edgy colours work well with cooler tones.
And of course, you can play around with colour combinations, such as dark hair with lighter tips.
Beyond following the instructions on or in the box, keep these handy tips in mind.
For long lasting hair dye, avoid washing your hair in hot water (a cool to warm temperature is better, and wait to wash your hair as long as you can).
Do a strand test first: Snip off a tiny bit of your hair and mix up a very small amount of the powder and developer and see how it turns out on your particular hair colour.
You should always carry out a patch test on an area of your skin to make sure you don’t have any kind of skin reaction to the dye.
For permanent hair dye to work, you have to mix it with the developer-activator that is included. You can save some of the hair dye for later use, but it must be unmixed.
When rinsing the hair dye out, keep at it until the water runs clear. Otherwise, you risk staining your pillows or clothing.
Holland & Barrett sell both henna and hair dye.
Choosing between the two is very much a matter of convenience and colour preference.
Henna is completely natural. When used on its own, it will make your hair an orange-red, if you are starting from grey or bleached hair, or it will give brown hair a red tint, and black hair a red glow.
But, by adding other natural ingredients, henna can also be used to dye hair brown or black.
Henna has three great benefits: it doesn’t fade as quickly as the other dyes; it strengthens and conditions your hair, and it is translucent. It blends over the colour you already have, so there is a certain seamlessness when dying your roots.
Henna should be left in for at least four hours, for a good strong stain, and for a deep red colour (rather than orange) you will want to do this process twice.
The easiest thing to do is apply before going to bed and cover your hair in glad wrap, a plastic bag, or a shower cap, then wash off in the morning.
Hair dye on the other hand, such as our Naturtint Permanent Hair Colour 5N Light Chestnut Brown, can be applied as part of your normal shower and hair-washing process.
It does tend to fade a little after a few months, but by then you will likely want to update your roots anyway.
Our hair dyes are without ammonia and are enriched with plant and seed oils to protect your hair and scalp. They come with a tube of multi-care mask to use after application and in the following weeks to help maintain the dye colour.