I have anaphylaxis via sesame & my only symptom (and of course the most dangerous) is my airways closing up, making it difficult to swallow anything for the next 24 hours. I understand that an allergic reaction is just the body releasing antibodies for a ‘non-threat’ but why does the body decide to close airways? This never happens when you are infected with a virus, so why does it occur during anaphylaxis?
In: Biology
Anaphylaxis is an over-reaction of your immune system caused by the activation of your antibodies.
This over reaction includes inflammation, which itself includes edema. Edema is a swelling that increases the blood flow in the affected region by dilating the blood vessels in order to flood the perceived threat with white blood cells and increase heat to disrupt microbes.
In anaphylaxis, this swelling is excessive and can block the airways, but also the esophagus and the mouth, and can also happen in the face, which is called angioedema.
Very basic explanation – Because anaphylaxis is a systemic reaction. Your body will recognise the allergen and mast cells start degranulating. You then have prostaglandins, histamine and other inflammatory mediators etc circulating through the body. In the airway, they cause constriction of the bronchi and bronchioles while the body releases secretions there as well. The result is your airway swells and you struggle to breathe.
Same pathophysiology causes your blood vessels to become permeable and fluid moves from inside the vessels to outside and your blood pressure drops, you get rashes and hives on your skin and you feel nauseous
It’s not so much that your body is deciding to do anything. Anaphylaxis causes extreme inflammation. Some people get itchy, some peoples’ hands swell up, some get rashes. You hit the jackpot with airway constriction.
If you’ve ever been congested and blew until your eyes popped but nothing came oit, that’s inflammation.
An allergy is not just a normal immune response to a false target. It’s an overreaction by only one branch of your otherwise quite complicated immune system.
If you have an infection like a cold, your immune system mounts a coordinated system-wide assault with all its branches.
If you have an allergy, only one branch of your immune system (histamine signaling) has a overreaction and mounts a localized solo-attack. One of histamine’s goals is to cause inflammation, which gives the rest of the immune system better access to attack to infection and repair damage. This causes swelling.
So, when you have an allergic reaction, your body doesn’t decide to close your airways. Histamine decides by itself it’s time to flush out the “infection” and the only way Histamine knows to do that is by causing inflammation which leads to swelling. If you’re unfortunate, that swelling happens to be in places you really don’t want to swell up… like places near your airways.
Note that histamine signaling isn’t only present in allergies. There are other infections, like an infected wound or pinkeye that cause a localized histamine response with swelling.
As others have said, anaphylaxis is a major and sudden immune reaction to something that shouldn’t cause any immune reaction.
Normal immune responses to something, eg an infection, result in white blood cells going to that area to fight the infection. These release certain hormones/chemicals to do the fighting and to attract more white blood cells to help fight it. This results in inflammation. One part of inflammation is swelling.
One of the chemicals release in inflammation is histamine. Histamine also plays a role in helping regular blood pressure and also how vasodilation blood vessels are. It has a role in how narrow or open our airways are.
There is release of many other similar chemicals too that all take part in continuing the immune response until the trigger is dealt with (ie infection gone).
In anaphylaxis, the response of the immune system causes sudden, inappropriate and massive release of these chemicals. Because there are high levels of them, the resulting effects are amplified. So, for example, lots of histamine will make our airways narrow, making it hard to breath. It can cause our blood vessels to dilate (relax and become wider) and so our blood pressure drops. Swelling occurs in various places, in your case it’s the throat and airways, so it reduces the space for air to flow and causes the difficulty breathing.
Treatment of anaphylaxis is adrenaline. This causes blood vessels to constrict and airways to open, counteracting the effects of the anaphylactic response.
Occasionally, a second dose of adrenaline is needed if the effects of the first dose don’t last long enough for the anaphylactic reaction to resolve. It’s why taking an antihistamine is also used in these reactions. It is slower working but reduces histamine release and resolves role reaction
With you finding it difficult to swallow for a day, it’s likely that’s the lining of your throat still to healing and returning to normal. This healing can include a bit of inflammation (appropriate inflammation though), so it might be worth using antihistamines for 24 hours if it happens again to see if it helps with the difficulty swallowing
Basically it all boils down to the normal things that happen when an immune response happens, but multiplied many many times, and happening very suddenly
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