Sweat primarily regulates internal temperature. Its appearance can offer insights into physiological processes. Most people associate sweat with being clear and colorless. However, sweat can sometimes appear in various colors, raising questions about its origin and what such changes might signify.
The Usual Suspect: Clear and Colorless
Sweat is primarily water (about 99%), with the remaining 1% consisting of solutes like electrolytes (sodium, chloride), which give it a salty taste. Other components include minerals, lactic acid, and urea. This composition contributes to sweat’s typically clear and odorless nature.
The human body contains two main types of sweat glands: eccrine and apocrine glands. Eccrine glands are distributed across nearly the entire body surface and are responsible for the majority of sweat production. These glands secrete a watery, clear fluid directly onto the skin’s surface, playing a primary role in thermoregulation. In contrast, apocrine glands are larger and located mainly in areas like the armpits, groin, and around the breasts. They produce a thicker, more viscous sweat that contains lipids, proteins, sugars, and ammonia, becoming active primarily after puberty.
When Sweat Changes Hue: Causes of Discoloration
While sweat is usually clear, various factors can cause it to appear discolored. One rare condition is chromhidrosis, characterized by the direct secretion of colored sweat from the glands. Apocrine chromhidrosis, the more common type, occurs when lipofuscin, a yellow-brown pigment, accumulates in apocrine sweat glands. The pigment’s oxidation state determines the sweat’s color, which can range from yellow, green, blue, brown, or black, typically affecting areas like the face, armpits, or areola.
Eccrine chromhidrosis is less common, usually resulting from ingesting certain dyes, medications, or heavy metals excreted through eccrine glands. Colors vary widely, including red, orange, yellow, green, blue, brown, black, or white, depending on the substance. For example, consuming large amounts of beta-carotene or certain medications can lead to such discoloration.
Another form is pseudochromhidrosis, where initially colorless sweat becomes colored after reaching the skin surface. This external discoloration often happens due to sweat interacting with chromogenic bacteria, fungi, or external chemicals and dyes. Certain bacteria produce distinct colors, such as pink-red, green-blue, or black-brown. Other external agents like fabric dyes, self-tanning lotions, or aluminum in antiperspirants can also cause discoloration.
Beyond these specific conditions, diet and certain medications can also influence sweat color or odor. While not typically causing vibrant hues, some foods like garlic or onions can alter sweat odor due to sulfur compounds. Medications, particularly those that cause excessive sweating, may also contribute to altered sweat appearance, though direct color changes are often linked to specific dyes or drug metabolites. Underlying medical conditions, though less commonly presenting as direct sweat color changes, can sometimes manifest as subtle shifts; for instance, high bilirubin levels in liver issues might lead to yellowish sweat.
When to Be Concerned: Seeking Medical Advice
Observing discolored sweat can be unsettling, and in some instances, it warrants medical evaluation. If sweat consistently changes color without an apparent external cause, such as contact with dyes or new products, consulting a healthcare provider is advisable. This is especially true if the discoloration is accompanied by other symptoms like pain, fever, unusual odors, or a general feeling of being unwell.
While many cases of discolored sweat are benign, it is important for a medical professional to rule out any underlying health issues. A doctor can help determine the specific cause, which might involve a detailed medical history, physical examination, or in some cases, laboratory tests. Addressing the root cause, whether it’s an infection, medication adjustment, or a rare condition, can help manage the symptoms and provide reassurance.