Guides
Evidence-based guides to the conditions and symptoms that viral infections leave behind.
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POTS
Postural orthostatic tachycardia syndrome (POTS)
Postural orthostatic tachycardia syndrome (POTS) is a condition that affects how your blood flow and heart rate respond when you change position, especially when you stand up. The name sounds complex, but it breaks down simply:
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MCAS
Mast cell activation syndrome (MCAS)
Mast cell activation syndrome (MCAS) is a condition in which your mast cells, a type of immune cell, become overactive and release their chemical "alarm signals" too easily and too often. When this happens, you can get sudden, repeated episodes of allergy-like symptoms in several parts of the body at once. The name breaks down simply:
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IST
Inappropriate sinus tachycardia (IST)
Inappropriate sinus tachycardia (IST) is a condition where your heart beats faster than it should, most of the time, even at rest. The heartbeat itself has a normal rhythm. It is just too fast for what your body is doing. The name breaks down simply:
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Orthostatic dizziness
Dizziness when you stand up
Feeling dizzy or lightheaded when you stand up is very common. Often it is harmless and passes in a few seconds. But if it happens often, lasts longer, or comes with other symptoms, it can be a sign that your body is struggling to control blood flow when you are upright.
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Orthostatic tachycardia
A fast heart rate when you stand up
Your heart rate naturally goes up a little when you stand. But if it jumps a lot, stays high, or comes with dizziness, a pounding heart, or exhaustion, it can be a sign that something is not working as it should. This guide explains what is normal, what can cause a high heart rate when standing, and how to find out more.
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Brain fog
Brain fog
Brain fog is a common term for daily thinking struggles, like having trouble focusing, remembering details, or finding the right words. Brain fog often happens after an infection like covid, or alongside conditions like POTS and ME/CFS. It can make everyday tasks, like reading, working, or having a conversation, feel exhausting.