Is there anything I can do to help my dog's itching before I take her to the vet?

She has been scratching a lot for the past week. Her diet is hypoallergenic, but it could be an allergy to something other than food, like gr pollen or some detergent. We've tried her on grain-free food for a few days to no avail.Her belly is very red from scratching. We've tried washing her and used Frontline. We cannot afford to take her to the vet right now, but we want to know if theres anything we can try in the mean time or if anyone has any suggestions as to what could be causing it.