My mum accidentally gave my 1 month old baby boy my daughter's Nan kid 4 formula!! Is there anything I can do or should be looking out for? TIA

If it's just once, should be okay. Has happened to my Cousin where she gave her 2 month old formula meant for her 3 year old by accident. Nothing happened, thankfully. You should watch for any development of rashes or excess bowel movement. Please be careful next time round.