Sensory overload is not often talked about, and in truth, anyone who has Adhd, Autism, or a sensory processing disorder could have one.
They can lead to panic attacks, meltdowns and burnouts, and are often difficult to deal with in a socially acceptable way, unfortunately. Anyway, here is what they feel like, which honestly depends on which sense is being overwhelmed.
Just a note: This is from my own, personal experience. No two people experience this kind of thing the exact same way, and feel free to comment your own viewpoints below
Often I will get a headache
When there’s too much light (or noise or really any sensory input, bar maybe texture) in a room, some people may just squint and complain a bit. For me, I will almost always feel physically in pain, making it hard to concentrate, and no - I do not need to drink more water, mother.
The amount of sensory input overwhelms my brain, and it physically pains me, in the end. If I realise what is happening, I will often leave the situation, but sadly that isn’t always possible, and I will usually close my eyes for extended (abnormal 
) periods of time if light is the issue, or try stimming to distract my brain. Although maybe I should, I rarely cover my ears, mostly because masking doesn’t allow me too unless it gets really bad
My anxiety peaks and it gets more difficult to remain calm
The overwhelm causes adrenaline to start flowing, and my brain starts to panic from all the input coming in. A whole bunch of anxiety symptoms; sweating, breathing shallowly/unsteadily, tics, will all start coming in. At this point, I am probably closing in on a panic attack or a meltdown.
It’s almost impossible to focus or concentrate
When a room is too noisy, I cannot function. I can hear every little conversation, every beep, the hissing of the lightbulbs and the tiny swishing and movement noises each and every person makes. The tiniest of noises are loud and my brain is hearing all of them. If someone is talking to me, I can’t understand what they are saying, because my brain is trying to understand everything else at the same time.
If I’m trying to do work and people are moving around, or there’s a mirror in the room, or it’s too bright - it’s not going to happen. This is even worse when said things are overwhelming.
Often I will disassociate or go non verbal
Click on the links for information on both of these states.
If the overwhelm gets too much, it is easy to lapse into one or both of these states, just to try and shut out as much input as possible, to allow the brain to relax a bit
All in all, a sensory overload is when your brain is overwhelmed by sensory input, and can last for minutes, hours, days or even weeks. Most of the time, when it comes to abating some of these things; it is best to find a less abrasive room or area and take a few minutes to do whatever you need to calm your body back down again.
That’s all, feel free to comment your own points, or any ideas on what I should write on next :]
Links to other "But What Does It *Feel* Like" Posts
Dissociation/Derealisation
Panic Attacks
Going Non Verbal
Ticcing and Stimming