I have a westie who has allergies. We have to give her a desensitizing vaccine injection every 2 weeks. She has had endless amounts of steriods and antibiotics over the years but this treatment although quite expensive is working! Every May when the grass pollen is high (or if she starts chewing her paws) we give her half a piriton tablet everyday to help her - our vet and the dermatologist recommended this. However, we have been told not to give the piriton one a day tablets, only to give her the normal ones.
Good Luck!