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It's getting pretty annoying constantly see people say things like, " the cold is good for my hair", "I need to dry up my scalp" and "this shampoo nourishes my hair."
Hair follicles are fed by your blood supply, but the blood vessels that feed hair follicles are very small and can be easily choked or clogged. When your hair is starved from nutrients and oxygen, it gradually gets thinner because the follicle is dying.
When your skin gets cold, it actually constricts. This means less blood is flowing to your scalp when you expose it to the cold. People like to claim that a cold shower nourishes their scalp, when they're really choking it off from the only thing that feeds your follicles. Its called vasoconstriction.
When you skin gets warm, the blood vessels expand, so that more blood is flowing to the surface of your skin and also your hair follicles.
However too much heat, like from a hot shower or a blow dryer will dry out the skin. When the skin gets too dry the cells shrink and the skin becomes tight and stiff. When your scalp is tight and stiff, the skin is squeezing your blood vessels, and your hair is being starved.
One of the reasons you guys might notice more shedding in the summer is because if you are sweating a lot then the lactic acid from your sweat could damage your hair follicles. Its your excess sweating that could be harming your hair, not the heat itself.
Also, if you're in the heat all day, you're likely going to be dehydrated. If you get dehydrated your blood becomes more viscous because it has less water, but it still has other contents. So now, your body needs to force this viscous blood through the tiny blood vessels that feed your hair follicles. This means your follicles might be getting poor blood circulation.
Another reason you might notice your hair being thinner in the summer is because you're actually letting your scalp get cold. Cold will cause the skin to vasoconstrict, even if the rest of your body is still warm. Your body temperature is usually close to 98.6F or37C. You might do an intense work out in the heat, and then immediately cool off in a breezy air conditioned room with a chilly 68 F. Your hair and scalp is still soaking wet, so it immediately becomes cold as you cool your self off. When it becomes cold, the blood vessels to that area of skin constricts. To make matters worse, some of you guys might pour a bucket of ice water over your head before cooling off, and then take a cold shower and step out into a cold air conditioned room.
If you live in a very dry climate where it is over 100F outside and the humidity is below 10 percent, your scalp is probably getting very dry even if you are sweating. Remember that water evaporates, but salt does not, so what you're left with is a dry, tight and salty scalp. Salt itself will change the concentration inside cells, causing them to shrink and this will make the skin even worse.
In the winter time, I also see people doing things that will make harm their hair follicles. In the winter its cold so you would probably put on a hat, but most cheap hats, beanies, skullies, etc are made our of polyester, nylon, and acrylic. These synthetic fabrics can cause hair to thin. https://www.ncbi.nlm.nih.gov/pubmed/8274779
To make matters worse, the hat might be too tight, so you end up pulling a tight hat over your head that's choking out your scalp at the same time. What you need to wear is a thick but loose hat that is made of wool or cotton, but those are hard to find.
If you don't war any hat at all during the winter then your head is scalp is going to get cold. When it gets cold, the blood vessels will constrict and your follicles will be starved. To make things worse, you might be wearing thick pants, a coat, and gloves so that the skin all over the rest of your body is flushed with warm blood while your scalp is starving. Most of you don't have hair that is long or dense enough to actually keep your head warm.
Some people like to take very hot showers or baths or go to a sauna in the winter time to warm up. They might get hot for a short while, but as soon as the hot bath or whatever is over, your body is now more sensitive to the cold than it was before you took the hot bath. What you need is consistently warm, but not hot place to stay.
Another thing I notice in bald people is that they tend to have loose,wrinkled skin on their forehead and faces, but they have very tight and shiny skin on the top of their scalp. It looks like as the skin on your face gets loose with age, gravity pulls the skin down tightly from the scalp since the skin is too loose to support itself. Maybe the scalp is getting pressed tightly against your skull and that reduces your overall blood flow to your follicles.
Anyway, I'm just theorizing stuff here.
TLDR: Cold makes your blood vessels constrict. A dry/ tight scalp chokes your follicles. Don't get dehydrated. Don't let the lactic acid buildup, wash your hair. Keep your scalp warm.
Hair follicles are fed by your blood supply, but the blood vessels that feed hair follicles are very small and can be easily choked or clogged. When your hair is starved from nutrients and oxygen, it gradually gets thinner because the follicle is dying.
When your skin gets cold, it actually constricts. This means less blood is flowing to your scalp when you expose it to the cold. People like to claim that a cold shower nourishes their scalp, when they're really choking it off from the only thing that feeds your follicles. Its called vasoconstriction.
When you skin gets warm, the blood vessels expand, so that more blood is flowing to the surface of your skin and also your hair follicles.
However too much heat, like from a hot shower or a blow dryer will dry out the skin. When the skin gets too dry the cells shrink and the skin becomes tight and stiff. When your scalp is tight and stiff, the skin is squeezing your blood vessels, and your hair is being starved.
One of the reasons you guys might notice more shedding in the summer is because if you are sweating a lot then the lactic acid from your sweat could damage your hair follicles. Its your excess sweating that could be harming your hair, not the heat itself.
Also, if you're in the heat all day, you're likely going to be dehydrated. If you get dehydrated your blood becomes more viscous because it has less water, but it still has other contents. So now, your body needs to force this viscous blood through the tiny blood vessels that feed your hair follicles. This means your follicles might be getting poor blood circulation.
Another reason you might notice your hair being thinner in the summer is because you're actually letting your scalp get cold. Cold will cause the skin to vasoconstrict, even if the rest of your body is still warm. Your body temperature is usually close to 98.6F or37C. You might do an intense work out in the heat, and then immediately cool off in a breezy air conditioned room with a chilly 68 F. Your hair and scalp is still soaking wet, so it immediately becomes cold as you cool your self off. When it becomes cold, the blood vessels to that area of skin constricts. To make matters worse, some of you guys might pour a bucket of ice water over your head before cooling off, and then take a cold shower and step out into a cold air conditioned room.
If you live in a very dry climate where it is over 100F outside and the humidity is below 10 percent, your scalp is probably getting very dry even if you are sweating. Remember that water evaporates, but salt does not, so what you're left with is a dry, tight and salty scalp. Salt itself will change the concentration inside cells, causing them to shrink and this will make the skin even worse.
In the winter time, I also see people doing things that will make harm their hair follicles. In the winter its cold so you would probably put on a hat, but most cheap hats, beanies, skullies, etc are made our of polyester, nylon, and acrylic. These synthetic fabrics can cause hair to thin. https://www.ncbi.nlm.nih.gov/pubmed/8274779
To make matters worse, the hat might be too tight, so you end up pulling a tight hat over your head that's choking out your scalp at the same time. What you need to wear is a thick but loose hat that is made of wool or cotton, but those are hard to find.
If you don't war any hat at all during the winter then your head is scalp is going to get cold. When it gets cold, the blood vessels will constrict and your follicles will be starved. To make things worse, you might be wearing thick pants, a coat, and gloves so that the skin all over the rest of your body is flushed with warm blood while your scalp is starving. Most of you don't have hair that is long or dense enough to actually keep your head warm.
Some people like to take very hot showers or baths or go to a sauna in the winter time to warm up. They might get hot for a short while, but as soon as the hot bath or whatever is over, your body is now more sensitive to the cold than it was before you took the hot bath. What you need is consistently warm, but not hot place to stay.
Another thing I notice in bald people is that they tend to have loose,wrinkled skin on their forehead and faces, but they have very tight and shiny skin on the top of their scalp. It looks like as the skin on your face gets loose with age, gravity pulls the skin down tightly from the scalp since the skin is too loose to support itself. Maybe the scalp is getting pressed tightly against your skull and that reduces your overall blood flow to your follicles.
Anyway, I'm just theorizing stuff here.
TLDR: Cold makes your blood vessels constrict. A dry/ tight scalp chokes your follicles. Don't get dehydrated. Don't let the lactic acid buildup, wash your hair. Keep your scalp warm.
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