Medically reviewed by Vicky Davis, FNP
Written by Our Editorial Team
Last updated 5/28/2021
“Everything in moderation” may be a tired phrase, but it has certain generational values that apply today. It’s never a good idea to have too much stress, drink too much alcohol or eat too much sugar.
The same advice, unsurprisingly, applies to essential elements and supplements.
A lot of things that are good for your body are bad in excess—even including water—and selenium is just one of them.
But unlike some things (morphine) that might kill you when overdone, selenium can cause more subtle issues which may take time to show up.
Whether you’re newly taking selenium and wondering about potential problems like selenium sulfide hair loss, or suspicious you might have overdone it already, read on for all you need to know.
Selenium is a trace element you need, and is part of your essential functions. It plays an important role in reproduction, DNA synthesis and thyroid hormone metabolism, and it helps arm your body against oxidative damage and infection.
Your recommended intake of selenium, though, is pretty small. Adult men, for instance, should take around 55 mcg (micrograms) per day.
For context, infants need about 15 mcg, and women who are pregnant or lactating need between 60 and 70 mcgs on average.
Selenium can be purchased as a supplement, but it’s typically found in foods with high protein content: meats, cereals, grains, eggs, poultry, fish and dairy products are all rich sources of selenium.
You can be deficient in selenium, too—which can make you vulnerable to certain diseases, and it can also affect your fertility, exacerbate iodine deficiency, and potentially play a role in osteoarthritis development.
Selenium is also thought to play a role in preventing cancer, cardiovascular disease, thyroid issues and cognitive decline, so a deficiency isn’t your best bet.
It’s an important trace element that you need for normal healthy function and longevity. Problems can arise, though, if you consume too much, or take more than the recommended dose.
While a single daily overshoot of your recommended selenium levels probably won’t cause a lot of problems, chronically high levels can mess with your system.
According to the National Institutes of Health Office of Dietary Supplements, selenium overdose over time can cause issues and symptoms like bad breath, metallic taste in the mouth, nail brittleness, nausea, diarrhea, rashes, fatigue and irritability.
You might also experience nervous system abnormalities, or issues like mottled teeth.
And then there’s the selenium and hair loss problem.
Selenium can indeed cause hair loss and hair brittleness—two major issues for your mop.
According to a 2018 article, excessive selenium can actually both modify the hair’s structure as well as impair the hair cycle, causing a condition called telogen effluvium.
Telogen effluvium isn’t a complicated condition, but it requires some background to understand. Essentially, each hair on your head is currently in one of three phases associated with its growth cycle.
The primary phase is called the anagen phase, which is where 90 percent of your hair will be at any given time.
This is when it’s growing and producing more length. After that comes the catagen phase, which is sort of a wind-down for each follicle. This lasts just a few weeks, before the telogen phase begins.
The telogen phase is a sort of rest for your hair follicle; 10 percent of your follicles at any given time should be in this phase.
Telogen effluvium is essentially a state in which more than the normal proportion of your hair is in the telogen phase, and won’t return to the anagen phase.
Visually, it looks like even thinning across your entire scalp, making your hair look sparse.
Telogen effluvium is typically associated with stressors like weight gain, surgery, major stress or anxiety, or an overburdensome load of a trace element like selenium.
The condition is also thought to be common for people recently experiencing high fever, or childbirth.
The great irony here is that selenium has been linked to decreased hair loss in chemotherapy patients.
It has also been widely used in the form of selenium sulfide to treat scalp conditions like dandruff.
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The good news is that telogen effluvium is almost always a fully reversible condition.
In most cases, after the trauma has passed from whatever brought on the hair loss, the hair will return within a few months as the cycles begin again for the affected follicles.
But there’s a caveat here—stronger cases of hair loss due to selenium exposure have been reported.
In one case, a selenium alloy associated with copy machines was found to have caused more severe hair loss for a worker who constructed the machines for six months.
The selenium exposure was likely high due to the machine worker’s profession, and the alloy was likely different from what you’d find in foods and supplements. (Note: the full report was not available to us for this research).
There don’t seem to be similar cases reported, but if you work with copiers daily, an extra blood test to be on the safe side is never a bad idea.
With this exception aside, selenium sulfide hair loss is likely to reverse course once you’ve lowered your selenium levels back to a safe quantity.
First, stop taking selenium immediately if you suspect you’ve run into the trap of excessive doses and resulting hair loss. Next, contact your healthcare provider for treatment advice.
If you are indeed suffering from telogen effluvium, your hair will begin to grow back on its own, but you might consider speeding up the process with effective and proven hair loss treatment options.
A few products that are effective at regrowing hair according to the American Academy of Dermatology, including minoxidil and finasteride.
Likewise, finasteride is a hair growth medication which works as a hormone blocker that targets male pattern baldness-causing DHT.
Talk to a healthcare professional to see if either might help you.
Selenium is a great example of the good-and-bad balance for everything out there in the world of supplements.
Cancer-prevention benefits are great, hair loss and nail injuries not so much.
The appropriate next step, as always, is to talk to a healthcare professional about something like selenium supplements before starting to take one.
If you are indeed seeing signs of hair loss, consult a healthcare professional for that as well.
They’ll be able to help you diagnose the problem (selenium-related or otherwise) and follow their recommendations.