My Grandson Is 2.10 Years Old. He Can Count And

My grandson is 2.10 years old. He can count and recognise numbers up to 20, can say different shapes and colors, knows names of different animals and sounds they make, calls us by names but yet to talk. All his friends including younger ones are already talking. He is a picky eater and seems to have a skin problem that seems to be an allergy as local doctors' prescriptions don't seem to help. He's all the time itchy and small red bumps appear after scratching. While he appears to be itchy all over, he scratches even his palms and soles of the feet. He's skinny but not underweight. Please advise.