Here’s something you might not know about me: I’m obsessed with white teeth. I’ve tried several at-home whitening kits from affordable Crest Whitestrips to the pricier Go Smile. But only Zoom Whitening, which I used under the care of a dentist last year, has given me the pearly whites I desired. Of course the system that gives the best results is pricey, so when I received a Rembrandt Two-Hour Whitening Kit in a gift bag, I thought it’d be a cost-effective way to maintain my white smile.

Here’s something else you don’t know about me: I have crazy chapped lips. I started using Blistex recently because it prevents chapped skin from forming on my lips and makes peeling off any skin easy.

But what happened when I combined the Rembrandt teeth bleach with Blistex? A painful chemical burn. Ouch! Having used other teeth whitening systems, I knew that it was important to keep my lips moist during the process. Other times, I used simple Vaseline or Neosporin Lip Health or Rosebud Salve, and everything was all good. But this time, my logic must have been on hiatus because it didn’t occur to me that Blistex would be too harsh to apply to already sensitive lips. You see, a lot of saliva accumulates while you’re bleaching your teeth. Obviously, I wouldn’t swallow this saliva-peroxide mixture, and I didn’t want to hold it in my mouth for several 20-minute intervals. So I did what any good girl would do — I spit. And that’s how my lips were burned.

The burn wasn’t noticeable at first. The morning after I bleached my teeth, I awoke to find the corners of my mouth crusted with dry skin, and it was painful if I stretched my mouth open to eat or even yawn. So I applied some Aquaphor, which moisturized the area, but didn’t really help to heal my lips. I then switched to A + D Ointment, which in my mind heals all skin ailments. It worked as well as the Aquaphor, but I also noticed the rest of my lips were turning black with bits of splotchy pink. Not cute!

My best friend is the only person I’ve let see my lips without embarrassment, and he helped me figure out that mixing whitening chemicals and Blistex caused the chemical burn. He also suggested I apply authentic, 100 percent natural shea butter to my lips last night–and I definitely saw some improvement this morning. There are more splotchy pink areas, the top layer of skin is growing back, and I can move my mouth without pain.

This was definitely worse than the time I exfoliated right before applying a depilatory cream to my upper lip. I burned a layer of skin off that time too. Clearly, I have a problem with burning myself in odd ways … and now I know why my chemistry teacher wouldn’t let me touch the Bunsen burners after the first few classes. At least I learned a valuable lesson — Rembrandt Two-Hour Whitening Kit and Blistex do not go together.

What’s your worse beauty blunder story? Tell us in the comments.