has no relation with the G6PD deficiency
. Certain drugs can precipitate the deficiency but Cefaclor
is safe medication. As rash containing pus heals it goes through various stages, reddish rash is one of the stage. As your doc has diagnosed the case as dermatitis( infectious) continue with the same medication and be watchful if rashes are increasing or there is any deterioration in general condition of child.
Wish you and your child good health