Viewing a single comment thread. View all comments

InfernalOrgasm t1_iuhr71e wrote

The 3 phases of fever

Fever is your body’s way of letting you know something is wrong. In a way, the fever is helping to fight off your infection.

This happens in 3 phases.

Your body reacts and heats up

Your blood and lymphatic system make white blood cells, which fight infection. When you have an infection, you make lots of these cells. They work faster to try and fight off the infection.

The increase in these white blood cells affects your hypothalamus. This makes your body heat up, causing a fever.

In the early stages of a fever, you often feel cold and start to shiver. This is your body’s response to a rising temperature. The blood vessels in your skin tighten up (constrict), forcing blood from the outer layer of your skin to inside your body where it is easier to keep the heat in.

The outer skin layer then becomes cool and your muscles start to contract. This makes you shiver. Shivering produces more heat and raises your temperature even more.

The fever levels off

In the second phase of a fever, the amount of heat you make and lose is the same. So the shivering stops and your body remains at its new high temperature.

Cooling down

Your body starts to try and cool down so that your temperature can return to normal. The blood vessels in the skin open again, so blood moves back to these areas. You sweat which helps to cool the skin, this helps to cool down the body.

This phase of a fever may or may not happen naturally. You may need to have some medication to start it off, as well as treating the underlying cause of the fever.

Source

100

FiveDaysOfPoop t1_iuhvbnh wrote

So if the body is heating up to fight an infection are we not working against it by taking antipyretics?

27

Tagracat t1_iuhwyk8 wrote

Basically, yes. Fevers are functional in that the higher body temperature begins to denature the proteins in infectious agents, or otherwise makes it inhospitable for them to reproduce, which allows the immune system to finish mopping up. We should let fevers do their thing unless the person is suffering a lot of discomfort (with the understanding that being sick in itself is going to be uncomfortable, and the fever will make them achy and weak. Which is a good signal to rest and let the immune system work.)

If the fever starts getting really out of control (like 105F/40C or higher) it runs the risk of cooking our own proteins as well, causing brain damage, or causing cells that we should probably hold onto to go into apoptosis. That's when we should step in and be like "dude, back the hell off" and try to lower body temperature or encourage the fever to break before it busts something it wasn't supposed to.

43

concentrated-amazing t1_iuilw8b wrote

I always weigh this when I'm sick, because I have three related factors that make fevers much more difficult for me (30F).

I have MS, and that means:

  • One of my particular brain lesions is in my hypothalamus, which affects my body temperature and my perception of it.
  • My body temp going over about 37.5°C/99.5°F starts to make my other, previous symptoms come back/be worse, including dizziness, balance, and leg weakness. When I had a fever with COVID, I was literally clutching walls, back of chair, etc. to get from room to room. (Normally I don't have any walking issues, only when I'm too hot.)
  • I almost never sweat. It will occasionally kick in, with maybe 20% of the sweat I should/used to be able to produce. So I can't bring my body temp down without external help like water/ice or cold air. If I don't have access to these, I'm at risk for heat stroke.

Thankfully, I don't get fevers often, but when I do, they seriously kick my butt. My first dose of COVID vaccine took me 3 days to feel mostly normal and a full week to feel completely normal. I have had 4 doses now, and know to proactively take both naproxen and acetaminophen at their recommended highest dose/interval.

9

zbertoli t1_iui4zmm wrote

Pretty sure of you're close to 104 or higher you run the risk of dying. Gotta drop that fever. Or if you have a non productive fever like when you get a vaccine. It's doing nothing to help you in that case

5

Bulletorpedo t1_iujyp9p wrote

40C (104F) is quite normal, specially in children. I believe what they say here is to seek help if you have 40C for more than a few days. Any thing above 41C (~106F) or if you’re in otherwise bad shape and it’s probably a good idea to seek help sooner.

People are different though, some will have 40C and be in fairly good shape, while others can barely walk as soon as they go above 38.5C.

2

Zigazig_ahhhh t1_iuhw6eb wrote

Yes, that's correct. If I don't have anything pressing to do, I usually don't take fever reducing meds unless my fever is over 38°. low grade fevers aren't hurting me, but they are hurting whatever infection I may have.

15

InfernalOrgasm t1_iuhwg5o wrote

Our immune system is a bit outdated. Typically, we can treat the ailment better ourselves with proper medications and procedures. Back when our immune system developed, we didn't have any of these things. A fever damages your body, your brain, and your immune system wreaks a lot of collateral damage. In our early stages of life, a little collateral damage is better than dead. Nowadays, we don't need that collateral damage because we can just treat it ourselves.

Our immune systems are not perfect, but it's better than nothing.

1

0range_julius t1_iui7z6k wrote

>Typically, we can treat the ailment better ourselves with proper medications and procedures.

What? I object to this immune system slander. We've invented some great medicines, sure. But first off, your immune system is constantly watching out for infections and cancer and kills them before they get out of hand enough for you to even notice them. There's no way you could replace that.

When things do get out of control, we have medicine to help us out, but most of them won't just fix you by themselves, they work in tandem with your immune system. That's why people whose immune systems are wiped out are basically dead men walking. Not to mention the constant arms race with antibiotic-resistant bacteria.

The immune system isn't perfect (I'm well-aware, I have allergies and an autoimmune disease), but it's incredibly sophisticated, to the point that we still don't completely understand it, and our medical technology hasn't gotten close to making it obsolete.

18

InfernalOrgasm t1_iui8imv wrote

I don't really disagree; it is an incredibly complex, useful, and absolutely necessary system. But with the use of medications, we can prevent a whole host of side effects from the immune system. Why wouldn't you if you could? I don't recall ever saying any of the things you're implying I've said.

2

relom t1_iuhz79f wrote

Is that colateral damage only for high fevers or would a 38° fever do some colateral damage?

4

InfernalOrgasm t1_iuhzrcc wrote

Mostly high level fevers; but our bodies maintain a "body temperature" for optimal performance for a reason. Low grade fevers are not much to worry about.

3

Fiery_Hand t1_iuhs3oy wrote

Yesterday I had such a fever (unfortunately there wasn't any thermometer to measure it), that I had terrible shivers, first time so strong that all my muscles literally ached after 15 minutes. And my lips became purple, and fingertips. First time I've seen something like that.

I took paracetamol to fight it and went to bed early, slept under the blanket in uniform (soldier here) and was rather cold anyway until med kicked in and I've almost drowned in my own sweat.

22

Endoman13 t1_iuj0ij0 wrote

If you’re a soldier why not seek medical attention?

2

Fiery_Hand t1_iuj5neq wrote

It's a specific situation, where our warship required electrical supervision and there was noone who could replace me anyway.

I took leave of my duties quite early (around 6 PM, where I should be on legs until 10PM), took the med, sweated my butt and woke up 4:30AM in rather good shape and finished supervision. I'm already home, military is specific place where you sometimes grit your teeth to avoid massive inconvenience for a lot of people.

2

Nfalck t1_iuhxb09 wrote

Very informative and easy to understand, but the OP's question was entirely about this sentence, which you just glossed over without explanation: "This makes your body heat up, causing a fever."

What makes your body heat up? What mechanism is the hypothalamus controlling? Is is muscular contractions (shivering) or some other thermal process?

14

InfernalOrgasm t1_iuhye31 wrote

"Heat/thermal energy" is simply a measure of how fast tiny little particles are moving; the more work (energy) being done, the faster (hotter) the particles are moving. There are lots of reasons that cause the heat to go up (as outlined by another commenter here). Our bodies are doing A LOT of work; our bodies are constantly generating heat. This is why we sweat; heat transfers to the sweat and the sweat evaporates into the atmosphere, thus cooling us off. You can think of sweat like a biomechanical liquid cooling system. Under Armor clothes for sports works by absorbing the sweat into the material, which increases the surface area in which the atmosphere can evaporate it, cooling us off even faster. To raise our body temperature, all our body has to do is regulate how much energy is being lost to the atmosphere versus how much energy is staying in the system (our body); which it can do in all sorts of ways.

2

Nfalck t1_iuhzm38 wrote

Thank you! So the hypothalamus induces the fever primarily by reducing heat loss, e.g. by reducing blood flow to the skin surface and cutting off the sweat response, rather than increasing mechanical or chemical thermal generation? Or is it more of "there are lots of processes in the body that contribute to heat generation and heat loss, and the hypothalamus pulls all of them simultaneously?" Or is it that there are so many interrelated processes that it's not clear exactly which levers the hypothalamus is pulling, we just know that heat generation increases and heat dissipation becomes less efficient?

5

InfernalOrgasm t1_iui0e0h wrote

We have a pretty good idea of how the immune system works; but we know less about how it works than we do know how it works (as far as we know). It's mostly reducing the amount of thermal energy lost, but doing "more work" does inherently increase thermal energy. So it's probably a balance of all of that.

Here's a good YouTube channel that covers quite a lot of the immune system in a very layman's kind of way.

1