Flat flies!!

Hi everyone,

As I live beside a rambla, I take my dogs for their daily walks there and wonder if anyone knows an effective way of repelling flat flies (those horrible little biting insects that look a bit like flying spiders.  They are awful - they burrow under the dogs' hair and  it's so difficult to get them off.)

All the dogs are frontlined, but it doesn't seem to deter them!  I tried a different route along the track, but still they hunted us down!  Any suggestions?

Thank you!

Megan xxx