Poop and itching. About. pls help.

Hi..my toddler boy who is 2.5 years now is pooping very hard and I am concerned about his poop color. He drinks a lot of milk everyday and consumed a lot of white food since 2 days(banana, makhana & rice porridge, dragon fruit, some apple, jowar ravva upma and salt biscuits) since yesterday. He drinks around 500 ml milk daily. Also he had developed tiny bumps recently and itches a lot. His Paed has told that it happened due to tree's seed outside our house where he plays and prescribed us Atarax drops and Prucal lotion. But we didnt send him out yesterday and he still developed some bumps. I am attaching his poop and his skin rash on arm and thighs. He is super active kid. But this  am really worried about. pls help.