tetracaine

I'm just wondering if any other tattooists have had any experience with the topical anesthetic, tetracaine. i had a client that came in today who had already applied the cream (...without asking me...)... there was a nice, big red welt where she had applied it... i noticed an immediate difference in the skin... and im not too sure i liked it.. i've been looking around at information about it, but if anyone has any information on their actual experiences with it, i would love to hear.(especially as far as any long term effects on the tattoo itself..) thanks :)