U can start when baby is teething and putting everything in mouth. Though babies never put teethers but other things in mouth

<span style="color:#3B5998;"><b><a href="http://app.babychakra.com/article/2778">Yummy Cookies For Teething Babies (And You Too!)</a></b></span>

<span style="color:#3B5998;"><b><a href="http://app.babychakra.com/article/78">Teething Food: Juicy Rajgira Teethers</a></b></span>

in how many <u>months</u>

Yes you can. Many good brands available like mee mee, chicco