MY MOTHER HAS HAD A RASH FOR 4 MONTHS. SHE

MY MOTHER HAS HAD A RASH FOR 4 MONTHS. SHE WENT TO THE SKIN DOCTOR WHO DID A BIOPSY AND ALL COME BACK GOOD. HE GAVE HER A PILL TO TAKE FOR THE ITCH. SHE HAS HAD ALL KINDS OF BLOOD TEST AND ALL IS FINE. SHE DOES HAVE FOOD ALLERGIES WHICH TRIGGER SO OF THE RASH BUT ITS NOT GOING AWAY. SOMEONE SUGGEST THAT IT COULD BE SKIN LYMPHOMA. SHE DID HAVE STOMACH LYMPHOMA THREE YEARS AGO BUT HAS BEEN CANCER FREE. I BOUGHT HER AVEENO AND HYDROCORTOSION. NOT SURE WHAT TO DO NEXT?