Treatments to avoid darkening of the skin on neck
A dark neck is quite a common problem, especially among those whose natural skin color is on the darker side. Usually, this is simply a tan, and is the result of keeping this part of the body exposed to the sun almost constantly. Most of us today wear clothes that leave our necks exposed, particularly the back of the neck. Regularly spending time in the sun in such clothing results in an accumulated and extremely dark tan. As you are aware, when skin is exposed to sunlight, it produces more melanin; since melanin is a protective pigment, this increase in melanin results in added protection against sunlight, but it also results in the skin becoming darker. With regular exposure, your skin continues to produce more and more melanin, to the point where it is black in color, while the skin that tends to be covered, such as that on your torso, remains relatively pale.
There is an easy way to solve this problem, but it will take a long time. It is not possible to get rid of tan in a few days, or even weeks. If you have developed a very strong tan, it may even take up to a year to completely disappear. However, all that you need to do is protect the skin of your neck from sunlight. Start wearing collared shirts, and when this is not possible, apply an adequate amount of sunscreen on your neck. It may also help to wear a hat, which will provide shade to your entire head and neck, and possibly a bit of your shoulders too. Of course, whenever possible, you should simply avoid being outdoors during sunlight hours for too long. Some amount of exposure to sunlight is essential, but too much damages the skin.
In some cases, darkening of the skin of the neck may be due to constant friction and irritation. In such a case, constantly wearing collared shirts may itself be the problem, as the collar continuously chafes against the skin. Most probably, it is not the collar itself that is the problem, but the material of the shirt. Try wearing shirts of a different material, preferably soft, natural fibers.
In addition, you should gently scrub your neck with a loofah when bathing, and try regularly applying a mixture of lemon juice and honey. Lemon juice is a natural bleach, and the honey will balance the harsh, drying effect of the lemon while soothing and moisturizing your skin.