Selenium and Hair Loss: Why Balance Matters Both Ways
Last reviewed on 25 July 2026. We review our treatment guides every six months to keep them accurate.
Selenium is an essential trace mineral, which means the body needs it in tiny amounts to stay healthy but cannot make it for itself. It is a genuine part of hair health, so much so that it is one of the very few nutrients with an officially authorised claim linking it to hair. The important thing to understand from the outset is that selenium is dual-edged. Too little is not good for the body, and too much is a recognised cause of hair loss in its own right. With selenium, more is not better, and past a point more becomes actively harmful.
For a plain, independently maintained overview of what selenium does, how much you need and what happens if you take too much, the NHS page on selenium and other minerals is the best starting point, alongside the consumer fact sheet from the US National Institutes of Health Office of Dietary Supplements. Hair loss has many causes, so please treat this page as general information and speak to your GP or a pharmacist about your own situation before starting any supplement.
The idea to hold on to is the same one that runs through our guides to vitamin E and to which vitamin deficiencies cause hair loss. Correcting a genuine deficiency can help hair, because the shortfall was holding it back. Taking more of a nutrient once you already have enough does not push growth higher, and in selenium's case a sustained excess can tip into toxicity. Selenium deficiency is, in any case, uncommon in the UK.
What selenium does in the body
Selenium helps the immune system work properly, plays a part in reproduction and in making thyroid hormones, and helps protect cells and tissues from damage. It does much of this as part of a family of proteins called selenoproteins, several of which act as antioxidants, mopping up the reactive molecules that would otherwise harm cells. Because a growing hair follicle is one of the most metabolically active tissues in the body, that antioxidant housekeeping is one reason selenium gets talked about in connection with hair at all.
That is a plausible mechanism, and it is worth understanding, but a plausible mechanism is not the same as a treatment. Every cell in the body uses selenium, so the useful question is not whether hair follicles need it, because they do. It is whether people who already get enough grow more hair by taking more, and whether people who are genuinely short of it lose hair because of that shortfall.
Is selenium good for hair? What the authorised claim actually says
An authorised European claim says selenium contributes to maintaining normal hair; that means enough selenium keeps hair normal, not that extra selenium grows hair.
This is where selenium is unusual. It is the subject of an official European health claim, one of only a handful of nutrients allowed to make one about hair: selenium contributes to the maintenance of normal hair, authorised under Regulation (EU) 432/2012 on the advice of the European Food Safety Authority. That wording is carefully chosen and worth reading closely. It says selenium helps maintain normal hair. It does not say selenium grows extra hair, thickens hair, or reverses hair loss.
A maintenance claim like this means that getting enough selenium supports hair being normal. It is about preventing the effects of a shortfall, not about pushing growth beyond normal in someone who already has plenty. The claim can only be used on foods that are at least a source of selenium, and it is not a licence to megadose. So the honest answer to whether selenium is good for your hair is: yes, in the sense that your body needs it and going short of it is not good for you, and no, in the sense that taking more than you need has not been shown to grow hair and can cause the opposite.
Does selenium cause hair loss? Both ends of the scale
It can, and this is the part that surprises people, because selenium sits at both ends of the hair-loss story. A genuine deficiency is not good for the body, and at the other end a sustained excess is a well-documented cause of hair loss. The safe zone is in the middle, and for most people in the UK an ordinary diet already lands them there.
Selenium deficiency
Selenium deficiency is uncommon in the UK. The NHS position is that if you eat meat, fish or nuts you should get all the selenium you need from your diet. The people most likely to run short are those on kidney dialysis, people living with HIV, and people whose diet is built almost entirely on plant foods grown in selenium-poor soil, because the selenium content of crops depends on the ground they grow in. The authorised claim points in the same direction: because adequate selenium helps maintain normal hair, a real shortfall is one of the things worth correcting. For most people in the UK, though, deficiency is not the likely explanation for thinning hair. Low iron, thyroid problems and genetic pattern hair loss are far more common, which is why our guide to vitamin deficiencies and hair loss is a better first stop than a selenium tub.
Can too much selenium cause hair loss? Selenosis
Yes, and clearly. The NHS is explicit that too much selenium causes selenosis, a condition that in its mildest form leads to loss of hair and nails. The US National Institutes of Health lists the signs of getting too much selenium as a garlic smell on the breath, a metallic taste in the mouth, hair loss, brittle nails or nail loss, a skin rash, nausea, diarrhoea, extreme tiredness, irritability and nervous system problems. At very high intakes it becomes dangerous, with effects that can reach the kidneys, heart and nervous system, and in rare cases it can be fatal.
The clearest real-world illustration came from the United States in 2008, when a liquid dietary supplement was mistakenly manufactured with around 200 times the selenium stated on its label. In the published investigation of that outbreak, 201 people were affected, and among them hair loss occurred in 70 per cent, alongside fatigue in 75 per cent, diarrhoea in 78 per cent, joint pain in 70 per cent and nail discolouration or brittleness in 61 per cent. It is a stark demonstration that selenium in excess damages hair rather than helps it, and it is exactly why loading up on supplements is a bad idea.
Is selenium hair loss reversible?
For the milder, supplement-driven cases, the outlook is generally reassuring. Excess-selenium hair loss behaves like a shedding problem rather than a scarring one: the follicles are pushed to shed rather than destroyed, so once the source of the excess is removed and intake returns to a normal range, hair usually regrows over the following months, in the same way that other forms of stress-related shedding recover. Recovery tends to be slower and less certain after severe, prolonged toxicity. If you think you may be taking too much, the practical step is to stop any selenium supplement and any heavy Brazil-nut habit and speak to your GP or a pharmacist, who can check what you are taking across all your products, because selenium is quietly included in many multivitamins.
How much selenium do you need, and how much is too much?
UK adults need 75 micrograms a day for men and 60 for women; 350 micrograms or less from supplements is unlikely to cause harm.
These are national reference figures, not a prescription for your hair. In the UK the amount of selenium an adult needs is 75 micrograms a day for men and 60 micrograms a day for women. That is a tiny quantity, and an ordinary mixed diet usually supplies it without any thought. On safety, the NHS advises that taking 350 micrograms a day or less of selenium from supplements is unlikely to cause harm. The US authorities set an upper limit of 400 micrograms a day from all sources combined, and in 2023 European food-safety advisers set a lower ceiling of 255 micrograms a day for adults. The gap between what you need and where harm starts is real but not enormous, which is precisely why loading up is unwise.
There is no separate, higher dose of selenium for hair growth. Because no amount above your daily requirement has been shown to grow hair, the sensible target is simply enough, not more. If you are asking how much selenium to take for hair growth, the grounded answer is that the question itself is the trap: the useful goal is meeting the ordinary daily requirement, which most UK diets already do.
Brazil nuts and selenium
Brazil nuts deserve their own mention, because they are by far the most concentrated everyday source of selenium. A single Brazil nut can contain roughly 68 to 91 micrograms of selenium, which is around a whole day's requirement in one nut. Eaten occasionally, that is fine and even useful. Eaten by the handful every day, Brazil nuts can push you towards the intakes associated with selenosis, which is why nutritionists usually suggest keeping them to one or a few a day rather than treating them as a snack. The same balance logic applies to the other minerals people ask about for hair, such as zinc and iron: correcting a genuine shortfall can help, but piling on extra when your levels are already normal does not grow hair and can cause its own problems.
The bottom line
Selenium is genuinely part of healthy hair, which is why it carries an authorised claim for maintaining normal hair. But that claim is about keeping hair normal, not about growing more, and selenium is one of the clearest examples of a nutrient where too much is as much a problem as too little. Correct a proven deficiency if you have one, get enough from a normal diet, and do not supplement above your needs. If your hair is thinning or shedding, see your GP or a dermatologist and get tested rather than guessing, because the cause is far more often something other than selenium. It may be worth reading our guides to vitamin D and biotin alongside this one, as the same balance principle runs through them all.
If you are considering a hair transplant
If you are planning a hair transplant or any other surgery, tell your surgeon and your clinic about every supplement and medicine you take, selenium included, and follow the pre-operative instructions they give you. Clinics differ in what they ask patients to pause and when, so the safe course is to disclose everything and follow your own clinic's guidance rather than a general rule from an article.
Frequently asked questions
Does selenium cause hair loss?
Too much of it does. Selenium is essential in small amounts, but a sustained excess causes a condition called selenosis, and the NHS lists loss of hair and nails as one of its milder effects. In a documented 2008 outbreak in the United States, where a supplement was made with about 200 times the labelled selenium, hair loss affected 70 per cent of the 201 people involved. A genuine deficiency is uncommon in the UK, so for most people the risk to watch is taking too much, not too little.
Can too much selenium cause hair loss?
Yes. This is selenosis, and hair loss is one of its recognised signs, along with a garlic smell on the breath, a metallic taste, brittle nails, skin rash, nausea, diarrhoea, extreme tiredness and, at high intakes, nervous system problems. The NHS advises that 350 micrograms a day or less of selenium from supplements is unlikely to cause harm, so problems tend to come from very high-dose supplements or from eating large numbers of Brazil nuts every day.
Is selenium hair loss reversible?
In milder, supplement-driven cases it usually is. The hair loss is a shedding problem rather than a scarring one, so once the source of the excess is removed and your intake returns to normal, hair generally regrows over the following months, much as other stress-related shedding does. Recovery is slower and less certain after severe, prolonged toxicity. If you suspect you are taking too much selenium, stop the supplement and speak to your GP or pharmacist rather than waiting to see what happens.
Is selenium good for hair growth?
Selenium is needed for healthy hair, and it carries an authorised European claim that it contributes to the maintenance of normal hair. But maintaining normal hair is not the same as growing more. There is no evidence that taking extra selenium grows or thickens hair in someone whose levels are already normal, and taking too much causes hair loss. The benefit is in having enough, not in having more.
How much selenium should I take for hair growth?
There is no hair-growth dose of selenium. In the UK adults need 75 micrograms a day (men) or 60 micrograms a day (women), and most people get that from a normal diet without supplementing at all. Because more than you need has not been shown to help hair and can cause harm, the goal is simply to get enough. If you are worried about your levels, ask your GP rather than starting a supplement on spec.
Are Brazil nuts good or bad for your hair?
Both, depending on how many you eat. Brazil nuts are the richest common source of selenium, with roughly 68 to 91 micrograms in a single nut, close to a full day's requirement. One or a few a day is a fine way to top up. Eating a large handful every day, on top of other sources, can push your intake towards the levels linked to selenosis and hair loss, so they are best enjoyed in moderation rather than as a daily snack.
Can selenium deficiency cause hair loss?
A genuine deficiency is not good for the body, and because adequate selenium helps maintain normal hair, correcting a real shortfall is worth doing. But selenium deficiency is uncommon in the UK, where a diet containing meat, fish or nuts usually provides enough. If you are shedding, low iron, thyroid problems and genetic pattern hair loss are far more likely explanations, and a blood test through your GP is the way to find out rather than guessing at selenium.
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