Solids at 10 weeks old?

i have just taken my little girl who will be 10 weeks old tomorrow to the doctor as she has been unsettled and has a croaky voice for the last 2 days, he said she has mild gastric reflux, also a reaction to her immunisations last thursday and is going through a growth spurt, he suggested i give her a tablespoon of weetbix mixed with apple puree to help settle the gastric reflux and help with the growth spurt, but i am very reluctant as she is not even 3 months old yet and am worried if i do give her solids so young she will develop food allergies, anyone else given solids this young? She is currently solely on milk, thanks