Tuny bumps all over arms and legs...grass allergy?

[AprilM]

Hi. My son is 21 months old and since the weather broke, we have been taking him outside in the back yard a lot. On Easter, he was outside and was rolling around in the grass. The next day his upper neck broke out in a rash with tiny little red bumps ...(he has short hair so the nape of his neck was exposed) His nose also started running and he starting coughing that night in the middle of the night. We called the ped, and they said it sounds like he has a bit of a croup virus (from the way we described his cough...barky) and the rash was most likely from his skin touching the grass. He has a routine check up a few days later anyway, and his neck rash was clearing up, but now the tiny bumps were all over his arms and legs. At this point they weren't too too bad, the doc saw them and still said she thinks it is from contact from the grass.
Since our ped appointment, the little bumps seems to keep appearing. Just on his lower arms and legs though....the skin that was exposed to the grass. His runny nose is getting a bit better, he is still coughing at night. Today when he woke up, I swear NEW BUMPS are on his one arm and both legs. They are tiny little things. We went outside yesterday, and his hands touched some tree bark, but he had long pants and long sleeves on.....

Sorry for the novel! Anyone else's ds or dd experience this reaction to being outside in nature? I am just trying to be sure about what this is. Doc recommended hydrocortisone cream for the itch....any other suggestions?

Thanks!
PS, there has been no fever....