Hi Celine
This has to be some kind of skin disease. If you have done the basics like good flea control and if the rash is spreading. I would advise a diagnosis and treatment from a vet. The longer you leave it the slower the skin will be to heal.
Cathy Wickenden BVet Med MRCVS
Barton Lodge Veterinary Centre
1 Midland Road, Hemel Hempstead, Hertfordshire, HP2 5BH
Tel: 01442 216048 24 hours
[
www.bartonlodgevets.co.uk]