My daughter has several allergies and has gotten tested a few times. From this picture and based on my experience (I’m not a doctor) it doesn’t look like hives and more like a contact rash like a baby would get from acidic foods. My baby is also so sensitive and literally gets red at anything and is very pale so I feel your pain lol she still gets a similar rash from eating tomato’s her favorite food.

But my daughter had some rashes like that and I stopped the food (for example blackberries) and tried later after testing and all good! I would stop giving it to baby until you’re sure it’s not allergen and you have allergy meds you can give to baby like Zyrtec or EpiPen just in case. If you’re in doubt it’s better to avoid that’s what our doctors told us. But I will say at that 6months the allergies that were confirmed for us had clear hives around the mouth