Its highly unusual indeed to have a reaction to lamb
Lamb and pears are the 2 things considered super safe in allergy diets

As for the Homeopath giving Aluminium to counteract Aluminium toxiticity in a baby i would be very very dubious indeed that this Homeopath knows anything about Constitutional prescribing

However if theres Alzheimers cases in your family or others are sensitive to Aluminium then I can well understand your baby also being hypersensitive to Aluminium as I was and still am

Virtually all Food manufacturing plants and that includes those who produce baby foods or formula milk products have Aluminium Vats and Aluminium processing lines and in a sensitive person this alone can cause hell

I suggest you go right back to square one and only give your baby fresh food that you cook youself in glass or high quality stainless steel

On no account use Aluminium or non stick coated or even chipped enamel pans etc
Slow cookers, bread making machines , etc etc all have hidden Aluminium elements in them and the only way i can describe the effect is

Heat Aluminium and its properties transfer to the food via a form of radiation

Far too many elderly folk are crippled up in pain for the simple fact they still insist on using Aluminium cookware and that includes my Mother who claims Aluminium has not hurt her!!!!!!!!!!!!!!!!