My breastfed baby keeps itching herself.

It’s been happening for 10 days.

I THINK it might be because my MIL washed her clothes in fragranced detergent and then used fragranced fabric conditioner, despite me showing her baby’s Exocet Non-Bio 0% fragrance detergent (She used the Method brand fragranced stuff), however, what if it’s a food allergen? If I eat nuts, can that go through to her via breast milk and cause issue to her? The only other food she has is Cerelac. Could it be a wheat allergen? 3-4 weeks ago, I started adding Whole Earth super smooth peanut butter. Could it be a peanut allergy? She only itches her upper body ie belly , chest and arms - not legs or face - and she been making it go quite raw

She is teething too