Rainbow Sweat (and Where It Comes From)
Humans have two types of sweat glands on our bodies. Eccrine glands, found in their highest concentrations on the forehead, palms and soles, excrete mostly water and salts. These glands play the biggest role in the body's regulation of internal temperature, controlled by the hypothalamus. Apocrine glands excrete sweat that contains water, fats, byproducts of metabolic processes and wastes. These glands are found most highly concentrated around the genitals, underarms (axillae) and around the nipples and are triggered by emotional responses. Each type of sweat gland can be involved in chromhidrosis.
The amount, location and color of the sweat being excreted helps in diagnosis of the type of true chromhidrosis. Usually, apocrine chromhidrosis is seen in excretions on the face, the axillae and around the breasts [source: eMedicine]. Eccrine chromhidrosis may turn up on the palms or soles of the feet. Patients with eccrine chromhidrosis may excrete any color of sweat (as we'll see in a moment) and typically in large amounts. Cases of apocrine chromhidrosis typically involve a smaller amount of sweat, and it tends to appear around the nipples and underarms.
Apocrine chromhidrosis results in only yellow, green, blue, black and brown sweat. Here's why: The culprit behind apocrine chromhidrosis is lipofuscin. This is a pigment that is produced as a byproduct of the oxidization of lipids (fats) in some types of cells. Lipofuscin can be produced in the apocrine glands, and when it occurs in high enough concentration, it can color the sweat that's excreted by these glands.
When colored sweat is excreted as yellow, green or blue, diagnosing apocrine chromhidrosis is made simple. Physicians can examine the sweat and clothing stained with colored sweat under a Wood's lamp (an ultraviolet or black light). The lipofuscins phosphoresce in the light, revealing the cause. It becomes more problematic when the sweat is brown or black because, although the sweat is colored by lipofuscins, they've been highly oxidized when they reach that pigment and don't fluoresce under a black light.
To diagnose eccrine chromhidrosis (which is rarer than the apocrine variety), a patient history is a physician's best tool. In most cases, this type of chromhidrosis is the result of an intrusion of a foreign dye or pigment that the patient has ingested. The nurse from the last page was diagnosed with chromhidrosis resulting from a fondness of a particular packaged food that contained a tomato powder and paprika. It wasn't until her doctors questioned her that they were able to compare the food to samples of her colored sweat and identify the culprit. The ingredients were water-soluble and were being excreted by her eccrine glands.