My 15 year old (102 lb) was prescribed 15 days of prednisone for poison ivy, starting with a 40 mg a day dosage. 20mg in the morning and 20mg at night. for five days. Second five days he is at 20 mg a day, 10mg in the morning and 10mg at night, then third and last five days, one 10 mg pill once a day. Im concerned that this may be too haigh of a dosage. He is very athletic and runs for a team. He also has asthma... Will this effect his asthma and could it have and impact on his running abilities.