Are breath-holding spells concerning? it happenend to my 16 months son twice, once because he was afraid, & once after crying for sth he wanted

Not necessarily: This is a simple amplification of crying/fitting that often escalates if you pay a lot of attention to it. Once a kid knows it will grab your complete attention they may use it often.Although it often happens when they don't get their way, it can happen if they drop something & are frustrated.Avoid direct eye contact during events & monitor with peripheral vision. You can keep them safe that way.