▁character . ▁For ▁example , ▁if ▁a ▁person ▁has ▁chron ic ▁week ly ▁head aches ▁with ▁pressure ▁on ▁both ▁sides ▁of ▁his ▁head , ▁and ▁then ▁develop s ▁a ▁sudden ▁severe ▁thro bb ing ▁head ache ▁on ▁one ▁side ▁of ▁his ▁head , ▁they ▁have ▁a ▁new ▁head ache . ▁ ▁Red ▁flags ▁ ▁It ▁can ▁be ▁challeng ing ▁to ▁differenti ate ▁between ▁low - ris k , ▁ben ign ▁head aches ▁and ▁high - ris k , ▁dangerous ▁head aches ▁since ▁sympt oms ▁are ▁often ▁similar . ▁Head aches ▁that ▁are ▁possibly ▁dangerous ▁require ▁further ▁lab ▁tests ▁and ▁imag ing ▁to ▁diagn ose . ▁ ▁The ▁American ▁College ▁for ▁Emer gency ▁Phys icians ▁published ▁criteria ▁for ▁low - ris k ▁head aches . ▁They ▁are ▁as ▁follows : ▁ ▁age ▁younger ▁than ▁ 3 0 ▁years ▁ ▁features ▁typical ▁of ▁primary ▁head ache ▁ ▁history ▁of ▁similar ▁head ache ▁ ▁no ▁ab normal ▁find ings ▁on ▁ne uro logic ▁exam ▁ ▁no ▁concerning ▁change ▁in ▁normal ▁head ache ▁pattern ▁ ▁no ▁high - ris k ▁com orb id ▁conditions ▁( for ▁example , ▁H IV ) ▁ ▁no ▁new ▁concerning ▁history ▁or ▁physical ▁exam ination ▁find ings ▁ ▁A ▁number ▁of ▁characteristics ▁make ▁it ▁more ▁likely ▁that ▁the ▁head ache ▁is ▁due ▁to ▁potentially ▁dangerous ▁secondary ▁causes ▁which ▁may ▁be ▁life - th re aten ing ▁or ▁cause ▁long - term ▁damage . ▁These ▁" red ▁flag " ▁sympt oms ▁mean ▁that ▁a ▁head ache ▁war r ants ▁further ▁investigation ▁with ▁ne