Tail Chasing !

Can anyone tell me why dogs chase their tails.Is there a reason ?. Or is it just play.

Sometimes it can be habit or boredom...

Must be habit with Poppy dog then janey it is only a rare accassions she does it as she is never bored...
She has a very large thick rubber rugby ball called "Grabber" interactive ball bright green,it takes her near on over a month for her to get through,she loves it...There is always another new one in the cupboard for when she has chewed that one up,she spits every bit out...she has never been a destructive dog since we have had her..she only chews like mad at her Grabber ball,her teeth are so clean,we think because she chews away every day at it between sleeping,walking and eating...
But she is so amusing when she chases her tail,we thought it might have been because she had an itchy bottom and couldn't get to it.

Mostly it's play, but I would always discourage it as it can lead to OCD, and even self-harm!

Thanks to you all:)

I would discourage it as Caryll says it can lead to further problems, try distracting with a toy if your dog starts to do it.

Darcy does it very very occasionally but I discourage it straight away

I would also discourage tail chasing. Just distract her when she starts. My dog Sid clipped the end of his tail on the corner of a radiator while spinning and split the tip. As it started to heal it got itchy which made him chase it even more. Eventually he bit it so badly he needed about an inch amputated from the end.

Vinnie does it occasionally but as said I also discourage it straight away.  

The best way to distract FYI is to provide a more interesting alternative. I have found this to be helpful as Frosty can go into this on rare occasion.

Thanks again everyone...must say though it's only once in a while she chases her tail...
As far as I know we have not much to be concerned about,I was just wondering why some dogs do it...

I think they just enjoy it! 

Zeus does it whenever he's bored or he's not getting any attention from me but I always discourage it, as said above, it can lead to a habit/OCD.