LCD Leaking very sticky liquid

I have a 4 year old XPS 12 - the one with the really useful reversible screen.

Just recently I've noticed a very sticky liquid leaking out of one corner of the screen.  There are now bright and dark patches on the screen near where it's leaking. As well as round the screen the sticky stuff gets onto the base of the laptop where I rest my hands to type. lt's really hard to clean off and I'm worried it may be toxic.

There has been no physical damage to the laptop at all - it just started leaking.  Is this a common fault or is it a sign of a defect in the design and manufacture?

Is there anything that can be done to fix it?

Thanks

Mike G