I have very bad asthma. I didn't see anything in the DVD that alarmed me and my pharmacy never mentioned it -neither did my GP. I'll be honest, when I started in the first two or so weeks after every shake I needed my inhaler (must have been something in the shakes that aggravated my asthma) but after that I got no troubles at all. It's down to your sister. If she's worried she should talk to her GP.