Is it possible to use Fenistil and Zinnat at the same time?

A child of 7 years, from Monday takes the antibiotic zinnat. On Thursday morning, a red longitudinal spot appeared on the cheek. After a few hours, she did not pale. Fenistil drops and gel are administered. Helped. The stain turned pale. The next day about 3h. after the administration of the antibiotic as if it was red again and the same with the evening dose, after fenistil everything goes down. Is it an allergy to an antibiotic? She does not want to stop the antibiotic herself, it is 4dauth.on Monday there is a check-up at the doctor. The child does not complain of itching or other ailments. Can I continue to administer (2dni)fenistil and antibiotic?