Why is the immune system so fast to respond to allergens, but take days to fight off a legitimate infection?
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I think you are exposed to millions of pollen or dust particles all at once, so the immune reaction is immediately strong. But with diseases, you are only exposed to a handful of microorganisms, so the immune response is minor until the number of microorganisms becomes large.
In reality most of the things you notice as a “cold” or upper respiratory infection are a result of the body fighting the legitimate infection. Your body responding to an allergen is a different set of cells as well. The immune response to an infection involves specialized cells ( B and T cells, amongst others) which have to activate, develop, and replicate to get ready. Where as allergens trigger a cell that is already just sitting around (mast cells) waiting for something to do. The mast cells sense their allergen and dump histamine and other stuff. Depending on the strength of the response, and where the allergen is, affects the response from itching to full on throat closure and blood pressure decline.
An allergen is a simple particle. It will sit there and be easily attacked until neutralized. If your immune system never responded you’d be fine.
An infection is living bacteria or virus. It will reproduce as long and attack body functions as long as it can. If your immune system never responded you’d die quickly.
Your immune system fights off most germs as quickly as it responds to allergens.
Our bodies are invaded by germs constantly. Every breath you take. Every bite of food. Every cut in your skin brings germs into your body. Nearly all of these germs are killed within minutes or hours by immune cells that respond instantly.
It appears to us that infections take days to fight off because we only notice the ones that get out of control, but the overwhelming majority are so quick and painless we never even know the germs were there.
In addition to what others said, our body IS fast to respond to infections. You just don’t notice the symptoms for 2-3 days because the infection is being held back. As the pathogen grows and spreads, a larger and larger immune response is generated which gives you the fever, body aches, fatigue, etc. Certain organisms have traits that allow them to beat your immune system long enough to grow while others are destroyed immediately because your immune cells are constantly surveying for infections.
Allergens are proteins that your body is able to quickly recognize and react to. Sometimes our body assumes that they are more dangerous than they really are and they over react. Think of that as mixing up bee venom with scorpion venom. Sometimes the meat suit gets its priorities confused when it comes to similar proteins. When that happens your immune system causes a lot of collateral damage trying to neutralize the “deadly” proteins.
Bacteria on the other hand are living creatures that want to survive and reproduce. They can react to their environment and sometimes can change their metabolism rate depending on if they want to be efficient and release less waste products, or if they want to multiple quickly and make the environment less hospitable to other life forms.
And viruses are organic machines designed to do one function, and they do that one function well.
Both of these cell types produce byproducts, but with all of the other similar byproducts produced by our own bodies, and the tons of other living creatures inside of you, it’s pretty difficult to pick them out right away when a infection is struggling to take root. And even then your body has a different immune response depending on how many foreign “threatening” proteins are inside of your body.
If you have a similar cold virus that your catching for the second time, your body can quickly pick up on it and send out a appropriate response. If you don’t understand the proteins you might send out “scout” cells that try to figure out how to neutralize the foreign cells, and then they go back and signal your body on how to precede. If you are going to die soon if nothing is done, your body pulls out every single thing that it has. It thrown caution and efficiency to the wind and chucks every thing that might work. At that point either you stop the infection or you die.
But if your body immediately jumped into the most extreme response to any foreign matter then it would quickly exhaust itself and something as simple as a flu season or a splinter could become fatal. But if your body is unable to respond and escalate quickly enough than a virus could become unstoppable before you put the proper reaction in place. It’s a tough balance when it comes to fighting living creatures in your body.
“Fight” is the key word here.
Allergens trigger the immune system to respond, but they’re not actually harmful. Your cell cops swarm the area and then stand around doing nothing useful because there’s no real threat.
An actual infection is different. The cell cops show up and find an army of hostile foreign pathogens that must be hunted down and destroyed. These pathogens have devised a vast number of devious tricks to evade or defeat your immune system, and so it’s an actual fight that only ends when either you or the invaders are dead.
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