Here’s a beauty trend that can go horribly wrong: Hair extensions! They’re a hit with everyone from celebrities like Britney Spears and Rihanna, to every day moms. 

But Consumer Reports warns that long-term use can cause not-so-pretty, and permanent, side effects. Dr. Orly Avitzur is the medical adviser for Consumer Reports. And she says damage can happen within just a few weeks. Because over time, the weight and pressure of extensions can cause headaches, a bleeding scalp, and actually rip your real hair out, causing bald spots. It’s a condition called traction alopecia. And you’re at the highest risk of developing it if your hair is thin or weak to begin with, before adding extensions. 

One New York dermatologist says he gets a lot of patients coming in who are in the 20s, with serious scalp damage from wearing extensions for only 3 to 6 months. It even happens to top celebrities – like Jennifer Aniston, who has publically talked about her experience, in which her real hair broke off. 

The good news is that the side effects usually stop. And you can even reverse traction alopecia – if you take out your extensions as soon as you feel pressure on your scalp, or notice hair falling out. But some women, who ignore the warning signs, have permanent hair loss – even in their 20s. 

Generally speaking, experts suggest ditching the glued-in or sew-in extensions - and use clip-on extensions instead, which you can put in your hair for a few hours at a time.