When sweat appears brown, black, green, or any color other than clear, it is known as chromhidrosis, which translates simply to “colored sweat.” This rare phenomenon often has a specific, identifiable cause rooted in either the body’s physiology or external factors. Understanding the source of the color helps determine whether the issue is a benign, temporary reaction or a sign of a persistent glandular condition.
Classifying Brown Sweat
The phenomenon of colored sweat is categorized into two main types based on where the discoloration originates. This distinction is important for figuring out the correct cause and subsequent management. The two categories are True Chromhidrosis and Pseudo-Chromhidrosis.
True Chromhidrosis involves sweat being colored before it reaches the skin’s surface, meaning the cause is internal to the sweat gland. This type is generally rarer and often chronic, persisting for a long time. The colored sweat is secreted directly from the gland in its pigmented state.
Pseudo-Chromhidrosis, in contrast, occurs when initially clear sweat becomes colored only after it has been secreted onto the skin. This discoloration is caused by external agents coming into contact with the sweat, such as certain bacteria, dyes, or chemicals. Since the cause is external, this type is typically easier to resolve once the contaminating substance is identified and removed.
Understanding True Chromhidrosis
The internal cause of brown sweat, known as True Chromhidrosis, is tied to the apocrine sweat glands. These glands are mainly located in specific body areas, including the armpits, the groin, the areolae of the breasts, and sometimes the face. True Chromhidrosis usually becomes noticeable after puberty, which is when the apocrine glands fully mature and begin their secretory function.
The brown color results from an accumulation and oxidation of a pigment called lipofuscin within the secretory cells of these glands. Lipofuscin is a yellow-brown substance, a byproduct of the oxidation of unsaturated fatty acids within cells. While normal, people experiencing this condition have a higher concentration of this pigment in their apocrine glands.
The specific shade of the sweat, whether it is yellow, green, blue, black, or brown, is determined by the oxidation state of the lipofuscin pigment granules. Highly oxidized lipofuscin generally leads to the darker colors, such as dark brown or black secretions. Triggers like emotional stress or physical activity can stimulate these glands, causing them to release the pigmented sweat.
The resulting colored secretion may appear as it dries on the skin or clothing. Because the cause is physiological and internal, this type of chromhidrosis is considered chronic, though the intensity of the discoloration may fluctuate.
External Factors Leading to Pseudo-Chromhidrosis
When brown sweat is caused by external factors, it is classified as Pseudo-Chromhidrosis, meaning the eccrine sweat itself is initially clear. Eccrine sweat glands are the most numerous type, distributed across nearly the entire body, and their clear secretion becomes contaminated on the skin’s surface. One common cause is the interaction with chromogenic bacteria, which are organisms that produce colored pigments.
Specific bacteria, such as those from the Corynebacterium species, can mix with eccrine sweat and create a black or brown discoloration. This bacterial interaction is often localized and may be accompanied by a change in body odor. The discoloration is a result of the bacteria metabolizing components in the sweat, which generates the visible pigment.
Environmental exposure can also lead to discolored sweat, particularly through contact with heavy metals or industrial chemicals. For instance, workers exposed to copper dust or other metal compounds may secrete sweat that appears blue-green or brown due to the metal salts dissolving in the sweat. This type of contamination often affects large surface areas of the skin that are exposed to the environment.
The third major cause involves chemical and dye contamination from topical products or clothing. Contact with certain fabric dyes in new clothing or the use of specific topical medications or self-tanning lotions can react with the clear eccrine sweat. This reaction can result in a brown stain on the skin or clothing that is often easily wiped away with a swab.
Seeking Diagnosis and Managing the Condition
A medical professional can determine the cause of discolored sweat through a careful history and a few simple diagnostic steps. The diagnostic process begins with a visual inspection and a detailed investigation of the patient’s lifestyle and environment to rule out any exogenous causes. The doctor may also mechanically express a small amount of sweat from the affected area to examine its color and consistency.
A Wood’s lamp examination is often used to distinguish between True and Pseudo-Chromhidrosis. The lipofuscin pigment responsible for True Chromhidrosis often shows a characteristic yellow-green fluorescence under this ultraviolet light, while externally caused discoloration may not fluoresce or will exhibit a different pattern. Microscopic examination of a sweat sample can further confirm the presence of pigmented granules or suggest a bacterial cause.
Management for Pseudo-Chromhidrosis focuses on eliminating the external source, such as using antimicrobial soaps or topical antibiotics to eradicate chromogenic bacteria. If a chemical or dye is responsible, avoiding the offending topical product or clothing item resolves the issue. For True Chromhidrosis, which is more challenging to treat, options aim to reduce the amount of pigmented sweat produced.
Medical interventions for True Chromhidrosis include the application of topical capsaicin cream, which can help desensitize the sweat glands, or in some cases, botulinum toxin injections. Botulinum toxin works by temporarily blocking the nerve signals that stimulate the sweat glands, thereby reducing the secretion of colored sweat. Although chromhidrosis is generally considered a benign condition, seeking professional confirmation is prudent to ensure no other underlying medical issue is present.