From a purely medical point of view...
A larp weapon has LESS chance of causing injury than either a bowling ball / game of lazer quest or even a tennis match... The most painful injuries for a LARP weapon to inflict seem to be pod shots & full face wacks! With luck folks wielding their larp safe weapons are striking in 'swinging' blows... NOT stabs... So so long as you keep your head up you will usually take one on the ear or top of the noggin at worst!!!
Making armour for the head is fun by the way!!! Look for 'bump caps' on line & in shops.... often simply a peak baseball cap... or bump cap insert... AMAZING little bits of kit like a helmet... Plastic & foam... A decent strike just staggers you... Very protective!!! (like wearing a hard hat!) I have been sewing the liners into cloth to make protective hats / headwear!!! (a female friend is making a wedding gown / veil one!)
Last thoughts though... Even a fairly heavy whack on the head isnt really that great a risk... However consider the following...
a) larp weapons are less soft & spongy in the cold! so avoid fights in winter / night time is u arent keen!
b) if gettin hit on the head REALLY bothers you, & for some I imagine it can be quite of-putting... Consider
surrendering!!! If your about to get attacked and think your up to your neck in it... then surrender / accept character wounds... make it clear you will accept hits! (hands up briefly... ok mate, K.O, i'm finished!!!)
c) Finally, if the idea of head injury is very worrying, consider being 'Non-combatant'... Theres a LOT more roleplay to larp than just fighting!!!
Worst ive taken was a falling platemail tower... 6ft odd of armoured shadow backhanding me in the lips as he fell over. It shook my world i can tell you!!! I may have even died, but i got better! :P
Crispin 'many-named'
Founder & Master Scribe of the Adventurers Charter