Hemoptasis can occur at any age. Airways are so inflammed that they often break and cause bleeding (obviously lungs are full of ateries and veins....their job is to exchange o2 in the blood).
Majority of research shows that hemoptasis is related to infection. But that's not always the case. Sometimes it can be stress, vitamin K defficiency, bronchaectasis (i can't spell), PMS (many women on here, including myself, when they have a bleed, it's exclusively a few days before their period) etc.
But regardless of the reason, it can become a harry situation if the bleed doesn't clot right away. Asphyxiation can occure and of course a great deal of permanent lung damage can as well.
A few teapoons, as I had, isn't always cause for alarm, depending upon your history. But in my case, I was still streaking the next day so my doc was concerned that my wound didn't fully heal. So observation in the hospital was in order in case I had a massive bleed and I needed to be embolized. IV antibiotics were started as well just in case it was an infection that was eating away at my airway.
I think I got my 1st bleed in high school. It's never really all that much.... except for one time I think. Anyway, It's happened to me usually when I overexert myself (which I did often when i was younger.... maybe 19-23ish... I'm almost 26 now).
So that's what the gig is. If you have more questions, i'd be happy to answer and I know many others on here would be happy to help as well who are more familiar with the issue.