Puppy is so itchy but isn’t old enough for Apoquel or anything similar

As the title says. My 4 month lpitbull/german shepherd pup has all the allergies. He eats Hydrolyzed salmon puppy food, some salmon training treats and that’s about it right now. We’re slowly trying to add more things to his diet but we’re struggling to find anything that won’t make him break out 😅. We have found that Zyrtec has helped immensely with his inflamed skin on his belly (Benedryl turned him into a complete lunatic!). The problem is, he is struggling to sleep through the night because even though his skin looks better, he still wakes up several times a night and just itches for 15-20 mins straight! Has anyone gone through something similar and have any advice for a dog mom lacking sleep??? Thanks!