Skin color is genetically determined although some lifestyle factors (like sunlight), medication and applications can alter it to some degree. However when these factors are removed, and if there is no damage to the skin, our skin color should return to normal as determined by our genetic makeup. Sometimes skin disorders arise where there is solely a problem with the color despite the lack of itching or a rash. These pigmentation disorders can work either way – causing the skin to become darker (hyperpigmentation) or lighter (hypopigmentation).
Why does skin color change?
The variation in the quantity of skin pigment, known as melanin, is responsible for the diversity of skin color among humans. Melanin also determines your hair and eye color. It is produced by specialized pigment cells, known as melanocytes, in the deepest layer of the epidermis (outer skin). More active melanocytes produce more melanin which is responsible for darker skin colors and less active melanocytes are responsible for lighter skin shades. It is not the number of melanocytes that make the difference but rather the activity of these melanin-producing cells.
Genetics are the main determinant of our skin color. But sun exposure is another important factor. Sunlight, and more specifically UV light, stimulates melanocytes to produce more pigment. This is the reason for tanning after bathing in the sun or using a tanning booth. On the other hand minimal sunlight exposure will reduce melanocyte activity. In both instances, UV light or the lack of it will only have a temporary effect on skin color. Some oral medication (capsules, tablets) and topical applications (creams and lotions) can also have this effect. Even hormonal changes, cigarette smoking and other factors can alter the activity of melanocytes. Sometimes changes in skin color are part of some disease or disorder and the cause behind the change in melanin activity cannot be conclusively identified.
Rash Vs No Rash
Most of us consider skin redness, swelling and roughness with itching as a skin rash. Some skin rashes may not itch at all. Nevertheless a skin rash is usually a result of inflammation in the skin. This inflammation can also affect pigmentation especially if its severe and/or long lasting. However, the skin conditions discussed below are largely non-inflammatory so there is no skin rash as most of us understand it. Skin hypopigmentation or hyperpigmentation still occurs.
Vitiligo (White Spots/Patches)
Vitiligo is a skin pigmentation problem where there is a gradual loss of pigmentation at certain parts of the body. It initially starts off as spots and grows into patches. These patches may grow larger and coalesce to affect large areas of the body. It is sometimes referred to as white skin disease. Vitiligo is incurable but there are cosmetic treatments that can reduce the impact of the condition. The exact reason why vitiligo occurs is unclear but it is noted that the number of melanocytes in the affected area is low. It could be an autoimmune-mediated destruction of melanocytes, abnormally short lifespan of these cells or some cellular defect.
Melasma (Dark Patches)
Melasma is a skin condition where dark patches form on the sun-exposed areas of the body and most commonly on the face. It is not the same as tanning or sunburn. As much as 95% of melasma cases are seen in women and it is largely associated with hormonal changes during the course of female life. It often occurs during or shortly after pregnancy or postmenopausal years. There is a strong family history and it is thought that certain cosmetics are likely to contribute to the condition. Here as well the exact cause is not known but it is believed to be due to a combination of factors – change in estrogen levels and sunlight exposure. It has been noted that there is an increase in melanocytes in the affected area.
Albinism (Total Loss Of Skin Color)
Albinism is an inherited disorder where the activity of melanocytes is extremely low or ceases entirely. As a result a person lacks normal skin pigmentation and it also affects the eye and hair color. Albinism is not a single condition but a group of disorders and in some varieties the skin, eye and hair color are almost normal. Most of us think of the form known as oculucutaneous albinism where skin, eye and hair color is drastically affected. People with this type of albinism are generally sensitive to the sun and have an increased risk of developing skin cancer. Symptoms like itching or redness may occur with sunlight exposure but usually there are no other symptoms beyond the lack of pigmentation.
Argyria (Silver Poisoning Blue-Gray)
Argyria is a condition where the skin appears a blue-gray color due to excessive consumption of silver. It is more commonly seen in recent years with the boom in colloidal silver as a health supplement. The discoloration of the skin can also affect the conjunctiva of the eyes and inner lining of the mouth. The silver deposition and darkening may also affect the internal organs as observed during an autopsy. The localized form is restricted only to certain parts of the body and often a result of topical exposure to silver. Generalized argyria occurs throughout the body and is more likely to occur with ingestive silver or from occupational exposure.
Linea Nigra (Pregnancy Abdominal Lines)
Linea nigra is a skin condition where a single dark line forms on the abdomen of pregnant women. It is a result of the disturbances in melanocyte-stimulating hormone (MSH) in the body. MSH stimulates the melanocytes to produce more melanin and in pregnancy this hormone may also be produced by the placenta. Most women find that it develops from the umbilicus (belly button) to the pubis but in some women it can run from the top of the abdomen. Symptoms such as discomfort, pain and itching are more often due to the stretching of the abdominal wall with the growing uterus and not due to the hyperpigmentation.
Adrenal Gland Disorders
Hyperpigmentation may also be a symptom of adrenal gland disorders particularly where there is a disturbance of the adrenal cortex and its hormones. It may occur with overactivity (Cushing’s syndrome) or underactivity (Addison’s disease) of the adrenal cortex. Normally this part of the adrenal gland is controlled by ACTH (adrenocorticotropin hormone). ACTH has some chemically similarity to MSH (melanocyte-stimulating hormone) in terms of a common precursor molecule and both are produced in the pituitary gland. One type of skin darkening seen in these conditions is known as acanthosis nigricans and tends to affect the folds of the body like the neck, armpits and elbows.