The primary health risks for teen sex appear to be related to sexually transmitted diseases and pregnancy, see related link from the US Center for Disease Control.
I have seen newspaper reports on research indicating that females starting having sex very early, before age 14, have a significantly higher risk for Cervical cancer later in life, but I couldn't find an online reference.
Teen sex and health is a fairly wide topic, the related links could be a starting point.
Harmful
it is very harmful or harmful depending on your body
yaa its very harmful
lip kiss not harmful to health
No, it is not.
fluoride is harmful to your health because in can soften your bones and make them more able to be broken
is rat rat pee urine harmful to ur health and how harmfuk is it
No- but like anything, if consumed in excess it can be harmful to your health
Yes, it is harmful.
No all fats are not harmful to your body.
It's not harmful at all.
yes