Thirty years ago I suffered an anaphylactic shock. It was fairly mild as I didn't lose consciousness but I came close. I was rushed to the nearest hospital where a quick check found that my blood pressure was dangerously low. I was given cetirizine hydrochloride to combat the allergic reaction.

I don't know for certain what caused the sudden attack but I suspect that one of my work colleagues put something in my drink.

Anyway, I recovered within minutes but six months later all my hair follicles were dead. My hair was falling out in clumps. I lost every hair on my body and my fingernails were cracking. A consultant told me that I was lucky because an anaphylactic shock such as I'd experienced can cause the autoimmune system to attack anything or everything. For me, it chose the keratin-producing cells. But it could have attacked the pancreas (type 1 diabetes), the myelin sheath around nerves (multiple sclerosis), the heart valves or many other things.

So, a warning: having a "faint" after an injection might sound like nothing but it could be life-changing.

(Feel free to re-post this on social media.)