Hello, This looks like compulsive biting disorder in your child. It is not uncommon presentation in clinical practice and can be treated, so dont loose hope. The best way is to- 1. repetitively tell the child to stop it, give him rewards (like giving him one extra of his favourite cookie, or making him see his favourite cartoon for 10min more that day; or giving him a small pack of his favourite chips, etc.) when he dosent bite his nails for 10-20minutes (or whatever the minimum range of time applies to him); 2. you may aslo take away his one previlidge if he voilates the rules (e.g.- not giving him his favourite dish or not taking him out for walk or play that day); 3. praising him infront of everyone around when he dosent bite his nails for significant amount of time- this parents usually fail todo- they only tend to complaint bad behaviour to everyone but not appreciate good ones...so, do the opposite: praise his control of biting nails more often. It is wise to tell him the rewards and punishments before hand and then begun. 4. if celexa is not working, you may shift him to a different drug- clomipramine or fluoxetine and this may give better results in controlling te obsessiveness of biting. Wish you luck. Dr. Manisha Gopal MD Psychiatry