When sweat appears blue, it is often an alarming occurrence that prompts concern. While not typical, discolored sweat, including blue sweat, generally stems from identifiable physiological processes or external interactions. Understanding these causes can alleviate worry and provide clarity regarding this uncommon phenomenon.
Internal Factors Causing Discoloration
Blue sweat, a condition known as chromhidrosis, primarily originates from apocrine sweat glands. These glands, found in areas like the armpits, face, and around the nipples, produce a thick, milky sweat. The blue, green, yellow, or black coloration in apocrine chromhidrosis is attributed to a pigment called lipofuscin.
Lipofuscin is a yellow-brown pigment that accumulates in the secretory cells of these apocrine glands. The color, such as blue, depends on the oxidation state of this lipofuscin pigment; higher oxidation states result in darker hues. While the exact reasons for altered lipofuscin concentration or its oxidative state are not fully understood, this internal production by apocrine glands colors sweat before it reaches the skin’s surface.
Eccrine chromhidrosis, where the widespread eccrine glands produce colored sweat, is rarer. This discolored sweat is linked to the ingestion of certain water-soluble dyes, medications, or heavy metals like copper. The substances are absorbed into the body and then excreted through the eccrine sweat glands, leading to the unusual coloration.
External Factors Causing Discoloration
Sweat that appears blue can be due to external interactions on the skin’s surface, a condition termed pseudochromhidrosis. The sweat itself is colorless when secreted, but it acquires a blue hue upon mixing with external substances or microorganisms. This means the discoloration happens after the sweat leaves the gland.
Certain bacteria, such as Pseudomonas aeruginosa and Bacillus species, produce pigments that can turn sweat blue or blue-green on contact with the skin. For instance, Pseudomonas aeruginosa creates pigments like pyocyanin (blue) and pyoverdine (yellowish-green), resulting in a characteristic blue-green discoloration. These bacteria often thrive in moist environments on the skin.
Other external factors contributing to pseudochromhidrosis include dyes from clothing, certain chemicals, or contact with metals. For example, long-term exposure to copper can lead to pseudochromhidrosis. This discoloration is a surface phenomenon, distinguishing it from chromhidrosis, which originates within the sweat glands.
When to Consult a Healthcare Professional
Observing blue sweat can be concerning; consult a healthcare professional to determine the underlying cause. While often benign, identifying the reason for discolored sweat is important to rule out less common underlying conditions. A doctor can distinguish between chromhidrosis and pseudochromhidrosis, which guides appropriate management.
During a consultation, the healthcare provider takes a detailed medical history, inquiring about the color of the sweat, affected areas, and potential triggers. A physical examination is also performed, and the doctor may press on areas rich in apocrine glands to observe sweat production and its color. Diagnostic steps may include a Wood’s lamp examination, using ultraviolet light to check for fluorescence of lipofuscin pigments, which helps confirm apocrine chromhidrosis.
To exclude other causes, the doctor might order tests such as fungal and bacteriologic cultures of the skin to identify pigment-producing microorganisms, especially if pseudochromhidrosis is suspected. Blood tests, including complete blood cell counts, liver function tests, and bilirubin levels, may also be conducted to rule out systemic issues that could manifest as colored sweat. This diagnostic process helps ensure an accurate understanding.