Sweating is an important bodily function that keeps you cool during hot weather and tough workouts. The end result is usually nothing more than sticky skin and the occasional pit-stained tee — but for a small percentage of people, sweating can also leave behind a blue toilet seat.
The phenomenon might be thanks to chromhidrosis, a rare skin condition marked by the production of colored sweat (think: blue, green, yellow, red, brown or black).
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According to the International Hyperhidrosis Society, there's very little data on the condition, making it difficult to pinpoint exactly how many people are affected and whether there's a link between chromhidrosis and things like race, sex, occupation, geographic location or the weather.
Here's what experts have managed to suss out about this puzzling skin condition so far:
There Are Three Types of Chromhidrosis
Apocrine, eccrine and pseudochromhidrosis each show up a bit differently and have their own underlying causes, Daniel Friedmann, MD, board-certified dermatologist at Westlake Dermatology in Austin, Texas, tells LIVESTRONG.com.
1. Apocrine Chromhidrosis
Apocrine chromhidrosis affects the areas of the body that contain apocrine sweat glands. These glands are in the underarm and genital regions, as well as the scalp, torso, eyelid, outer ear canal and nipple areas.
"All apocrine fluid contains yellow-brown granules called lipofuscin," Dr. Friedmann says. "For people with apocrine chromhidrosis, these secretions contain a greater concentration of highly oxidized lipofuscin granules, giving them a significantly darker green-brown to blue-black color."
Because apocrine glands don't start functioning until puberty (when hormonal stimulation begins), this form of chromhidrosis is typically more prominent when a person is younger, with symptoms becoming less severe as they age (as apocrine secretion tapers off).
2. Eccrine Chromhidrosis
Eccrine glands are found almost everywhere on the body (except for the outer ear canal, lips and certain areas of the genital region) and they're especially concentrated on the forehead and cheeks, armpits, palms and soles of the feet.
They're the sweat glands responsible for controlling body temperature, keeping skin hydrated and protecting the skin barrier.
Eccrine chromhidrosis may be caused by something internal, like an infection or excess bilirubin (an orange-yellow pigment formed in the liver), or external, like the ingestion of certain substances, Dr. Friedmann says.
Those substances might include water-soluble dyes, heavy metals (like copper), excess food coloring or flavoring, as well as certain medications (rifampin, an antibiotic; quinines, an antimalarial; and levodopa, a dopamine precursor used to manage Parkinson's).
It's thought the excess pigments from these internal and external sources make their way to the eccrine glands, where they're excreted along with perspiration, ultimately blending together to create colored sweat.
"Because of its wide range of underlying causes, eccrine chromhidrosis can happen at any age," Dr. Friedmann says.
Pseudochromhidrosis can also happen at any age and stem from a variety of causes — all of which are external in nature.
This form of colored sweat is seen when normal perspiration at the skin surface interacts with other compounds, such as dyes (from a new pair of jeans, perhaps), chemicals (a la sunless tanning sprays) or chromogenic bacteria on the skin (bacteria that produce pigments), Dr. Friedmann says.
In other words, it's not your sweat that's colored — the color comes from the way your sweat interacts with other things outside your body.
What About Chromhidrosis During Pregnancy?
Although there have been several reports of pregnant people turning their toilet seats blue, there's no research connecting chromhidrosis and pregnancy. Some people theorize that hormonal changes or certain ingredients in prenatal vitamins are behind the phenomenon, but we just don't have a clear answer. The condition is harmless, though, so pregnant people shouldn't worry about blue or purple toilet seats, although it's something you can certainly mention to your ob-gyn.
Treatment Options for Chromhidrosis Are Slim
Unfortunately, apocrine chromhidrosis is a chronic skin condition — symptoms can regress as you age, but there's no guarantee they will. The treatment options currently available focus on reducing symptoms as much as possible, but there's no cure.
Apocrine secretion can be triggered by emotions (stress and anxiety), rubbing of apocrine-heavy areas (friction from clothes) and hot showers and baths, so doing what you can to reduce these triggers — practicing mindfulness, wearing breathable clothing, taking lukewarm showers — can be a solid first step.
The primary treatments for apocrine chromhidrosis are topical agents — antiperspirant (such as Drysol), to temporarily plug the pores causing you trouble, and capsaicin cream, to deplete nerve cells of Substance P, "an important chemical that controls aprocrine gland secretion," Dr. Friedmann says.
If topical products are irritating to your skin, another option is Botox injections, which block the nerves that stimulate the sweat glands, with dryness lasting anywhere from four to 12 months. There are also a few options for pills that can decrease sweat production.
Manual expression of the apocrine glands (where you carefully squeeze the glands to empty them, similar to how you'd pop a zit) can also offer relief, but the results only last up to a few days. Ditto for manual pressure (pressing down to express the glands) to improve the look of the affected area, with results lasting only 24 to 72 hours.
Treatment options for the other two types of chromhidrosis are more promising, though: "Eccrine and pseudochromhidrosis may completely resolve once the cause is avoided or treated," Dr. Friedmann says. "Finding and stopping the specific cause is paramount."
This process might involve your doctor testing skin scrapings, secretion smears and extraction samples from clothing. Once the cause has been confirmed, they can help you determine the best course of action: ghosting the culprit, treating it (with antibiotics, for example) or replacing it with another option (say, a different medication) that doesn't trigger colored sweat.
Is Chromhidrosis Something You Need to Worry About?
Chromhidrosis is a harmless skin condition, but because colored sweat can be a symptom of something more serious, it's important to check in with your doctor or dermatologist for an official diagnosis.
"Your doctor can run the necessary tests to rule out more serious causes of colored sweat, such as infection, jaundice, hematidrosis (bloody sweat) and poisoning," Hadley King, MD, New York City-based board-certified dermatologist, tells LIVESTRONG.com.
Tracking your daily activities for two to three weeks — such as what you've eaten and any chemicals you've come into contact with as well as vitamins, supplements or new medications you're taking — leading up to your doctor's appointment can be helpful in determining your triggers and what the potential culprits might be.
It's also important to talk to your doctor about any emotional distress you're experiencing in relation to your chromhidrosis, as feeling self-conscious about it is totally normal, Dr. King says: "Although it's a rare condition, you're not alone — there are therapists and counseling available to help you out."
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.