I’ve only been using Huel for a week and and a half, first delivery was banana and vanilla.
I’ve been alternating the flavours each day but have found the vanilla causes major headaches!
It was so bad yesterday and lasted over 2 hours of head splitting pain!
What on earth could be causing this?
How is your hydration on the daily?
Really good, I’ve found I need to drink more since starting Huel.
I’ve never had a headache after a vanilla huel. Maybe there is other reason - e.g. some food supplement? Maybe it’s just a coincidence?
Ok. I’m wondering if it’s sugar withdrawal? Cannot think of any other reason tbh especially given you’re on top of your hydration. Have you gone 100% or having other food too?
Caffeine withdrawal ? 
Thanks for your replies,
I’m not taking any other food supplements.
I’m only having Huel for breakfast and am eating healthy meals for the other two. I’ve never been a big coffee drinker, preferring black tea and that hadn’t changed.
Its also only on the days I have vanilla, so I’m going to chuck it out and stick with the banana. What a waste of £20!
Same happened to me- my first two bags were chocolate and vanilla, no problems with the chocolate but dreadful headaches on the days I had vanilla. I managed to finish the bag (mixing the two flavours helped), the headaches didn’t persist, but I’ve avoided vanilla since!
There are a lot of possible reasons for headaches. As mixing solved the issue it can’t be an allergy or intolerance. People with migraine often report to have certain “triggers” which might be light, a specific flavor, weather changes, change of sleep times and a variety of other things that don’t seem “logical” or for which there is no sufficient explanation.
In my opinion really very bad headaches should get an MRI especially to rule out vascular pathologies; in the end it’s up to you and your general practitioner - but I would contact him/her and talk about it.