Fingernails and toenails they’re not just for decoration they protect your fingers and toes and help you pick up tiny things like splinters or that piece of spinach stuck between your teeth after lunch.

They can also tell you a lot about your health nails are collections of dead cells that grow from a root called a matrix hidden just beneath your cuticle.  The lighter crescent-shaped area at the base the matrix, constantly makes new cells called plate cells and each layer pushes the old dead plate cells out of the cuticle.

They’ll start to grow differently or even change color it usually means that there’s something wrong with the matrix or with the surrounding tissue.  So by working backward you can often figure out what’s doing the interfering and in the process maybe learn something about what’s going on in your own body bows lines.  For example our horizontal ripples on the surface of a nail they look like little waves and they form when the matrix stops producing new cells for a while.

The matrix starts making new cells again they push the nail out as usual but there’s an indentation marking the spot where it stopped kind of like a tree written there’s a reason why the matrix would have hit the pause button.  Probably, it wasn’t getting enough nutrients from the bloodstream.

Usually that means that the person has an infection or some other kind of serious illness body shifts its nutrient flow away from low priority activities like growing nails towards high priority activities like not die.  That’s why people who have high fevers for a while often develop bows limes a month or so afterward. Sitted nails are another potential matrix issue where the nail surfaces have indentations that look like very small potholes these pits are linked to skin disorders like psoriasis and eczema which can cause inflammation of the matrix and inflamed matrix produces new plate cells unevenly so you end up with depressions on the nail surface nails.

It can also change color something you’ve probably noticed if you’ve studied your nails on a cold day and realized they were blue.  Generally that means that your extremities aren’t receiving enough oxygen blood with low oxygen is darker and reflects light differently through your skin making your nails look bluish it could just be your body reacting to cold by constricting your blood vessels.  But a person whose blood isn’t receiving enough oxygen could have a respiratory illness like asthma or emphysema.

Blue nails can also be a sign of Raynaud’s disease a disorder marked by spasms in a person’s blood vessels that narrows the narrowing reduces blood flow to the extremities so they get blue nails now. Blue nails it’s not actually the nail changing color to the bed underneath it but nails can also turn yellow and that’s actually the nail changing color this can happen for a lot of different reasons in most cases it’s caused by a fungal infection known as a nickel mycosis.  Easter mold sets up shot within the actual nail plate turning it yellow it doesn’t smell too great either other times yellow nails means something more serious like yellow nail syndrome which doesn’t sound super serious. But it happens when the matrix does produce new plate cells but very slowly so they pile up and create a thicker yellowish nail plate but like BOS lines, yellow nail syndrome is caused by something else.

It could be a chronic respiratory disease which would reduce the nails oxygen supply and slow growth or it could be a sign of an issue with the lymphatic system which distributes protein-rich fluids throughout the body.

Usually that issue is cancer or AIDS a black or brown streak in a nail can also be super serious or nothing at all some people that Street can signal subungual melanoma a form of skin cancer that affects the nail bed which is the skin underneath the nail plate melanoma often changes the color of the skin including the skin under nails, so the streak also might be harmless if you have a darker complexion it’s completely normal.

One study 77% of black people over the age of 20 reported having a darker streak in their nail so it could be something or it could be nothing.  Which is why if you’re worried about the color or look of your nails here’s a tip don’t get all your medical advice from the Internet these changes can mean more than one thing so talk to a real doctor before jumping to any conclusions.

We are not a real doctor these are watching this episode of scishow which is brought to you by our patrons on patreon who give us money so that we can do this which is really nice if you want to help support this show you can go to and do not forget if you want to get smarter with us – go to and subscribe!

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