The short answer is NO. Oral sex on the male or female partner does not have any bad effect if both partners is healthy and std and infection free.
Depending on the age (and teen can really mean from puberty to 19), you have to be careful. Even oral sex is illegal under certain circumstances in most countries. This is especially true for ages under 16 or older male partners.
You also have to decide if she is morally old enough to become sexual in this way.