This depends on what your natural skin colour is and what has changed it. If you mean a suntan and how best to speed up the return to un-tanned skin, there are a few ingredients that can help. If you have lightened your skin and you want it to return to its natural darker shade, it depends on what you used to lighten it.
I will assume the former, let me know if that’s not what you were asking.
The skin will darken when the melanocytes deep in your skin release melanin to travel up to the surface skin layers to protect you from UVA and UVB radiation. When they meet, the skin’s pigmentation will darken (there is an immediate effect and another, delayed by two or three days, when the melanin continues to be produced).
If you stay out of the sun, this should fade in about two weeks, depending on how tanned you are, your age (the younger you are, the faster skin cells turnover, so the tan will go more quickly) and the condition of your skin - well hydrated, even textured skin will fade more quickly and evenly.
You need to stop any “more please’ messages getting to the melanocytes and then gently exfoliate the top, tanned layer of skin. You may be tempted to use lemon juice or some other harsh bleach, please don’t, the pH is far too low not to irritate your skin. In theory, you could apply yoghurt or lots of milk, for the lactic acid content, but I’m not sure how effective this would be, possibly a bit.
So, I would recommend apply a cream that includes 1. something to stop the melanin being formed and 2. an exfoliating ingredient:
- a-abutin - similar to hydroquinone at 1% (this helps switch off the message to the melanocytes); liquorice extract (the glabridin in the plant also inhibits melanin, but the amount of it in extracts does vary); soybean extract, again similar; Niacinamide (B3); mulberry extract (like many lighteners, this can be irritating); Kojic acid, gentle but effective. Some essential oils can be added to a fixed oil with good effect (alway use in dilution), but these can be irritating on naturally light or sensitive skin and must be used in the correct doses/mixture - seeRobert Tisserand for well researched, excellent advice on all things essential oil.
- Chemical exfoliants and physical exfoliants: AHAs or more gentle, PHAs (lactic acid, glycolic acid etc); Vitamin C does both 1 and 2, again use it in low concentrations and build up or you will irritate your skin; oats. For a physical exfoliant, you can simply use a linen or soft face cloth, if you’re prepared to pay more, a little spinning brush with soft bristles is very good; alternatively, cook rice until it is slightly soft and rub this into skin - the rice itself, like oats, is conditioning. You can buy little plastic beads, but we don’t need more plastic and things that dissolve work just as well.
Whichever you use, do moisturise you skin well afterwards as these are drying and can cause inflammation if you are over zealous. Try to be patient, and don’t scrub you skin; it is better to get a good, even result over two weeks that a very sore face after three days of AHAs and sandpaper!
- Don’t forget to wear a broad spectrum sun-screen! Apart from the obvious, many of the skin lightening ingredients will make your skin more sensitive to sunlight.