It is normal for teens to develop stretch marks during puberty or when they experience rapid weight gain, according to Teens Health. Both teen girls and boys are susceptible to developing stretch marks.
Stretch marks occur when there is a disruption in the normal production of the protein that makes up the skin's connective tissue. This protein is known as collagen. Stretch marks are scars that form when collagen production is interrupted by rapid weight gain and the stretching that the skin endures from weight gain. The use of steroid-enhanced ointments and creams can also cause stretch marks. Stretch marks tend to fade in time or at least become lighter.