What are the common causes of allergies in southeast Kansas this time of year?

My granddaughter is having a hard time with her allergies and asthma like reactions. Also she gets a rash (or redden of her face and hand/arms if her sleeves are short.) whenever she goes out in her backyard to swing. She is two years ago and loves to go outside; but we are worried it will become life threaten if we don't figure out what is causing her reactions. She can go to the park and the front yard without the rash or severe reactions. She does have some allergy problems but only the backyard causes scary reactions.