Brown spots on just half of the face are indeed a rare occurrence but it could just be something that is similar to an allergy or freckles of some sort. Color in our body is dictated by only one pigment called melanin created by cells called melanocytes. This is the reason why humans are colored only from a pale pink that is closer to tissue color to various shades of brown. Brown spots appear usually because of some kind of hormonal disturbance or due to skin damage from exposure to the sun. However this wouldn’t be the reason in your case as these spots are only on one side of your face. Whatever the reason is, you might have to wait for some time before your face naturally comes back into balance. It would also be a good idea to go to a doctor and get some tests done to check the levels of your hormones.
Skin darkening that result from a hormonal imbalance is usually because of either insulin or melanocyte stimulating the hormones or MSH. Insulin can sometimes cause skin darkening in a condition called acanthosis nigricans. This usually happens to people with Type 2 diabetes since there is a lot of free insulin floating around in the blood instead of being mopped up in the cells and tissues. This could stimulate the melanocytes to produce too much skin pigment and thereby create the appearance of brown tanned patches. MSH is a hormone that stimulates the melanocytes to create melanin. This is only secreted in high enough quantities to create a visual effect if you have already sustained exposure to sunlight. MSH can also be secreted because of the actions of other hormones as well. One of these hormones is estrogen. This occurs in a condition called melasma when sudden swathes of the skin turn brown. The condition goes away when the hormone levels stabilize.
A good way to prevent estrogen in your body from gaining the upper hand is to drink a lot of fresh cow’s milk. Cow’s milk contains progesterone that tempers the levels of estrogen in your body. For the darkening that has already occurred, you would need to bleach out the spots. This would require some strawberry pulp mixed with lemon juice to be applied as a face pack. Consumption of vitamin E in the form of green leafy vegetables would also help reduce the dark spots. Azelaic acid from wheat, rye, and bran is an equally effective remedy. Both vitamin E and azelaic acid suppress melanin production.
answered by M W