Is It Possible To Get Poison Ivy 9 Days After

is it possible to get poison ivy 9 days after contact? My son had some scrapes on his ankles but 9 days later woke up with severe red areas circling the cuts...which them developed into a pussy oozing infection. The doctor prescribe cephalexin...after 4 doses he had a rash all over his body. New doc..discontinued use saying he could be allergic to meds...also at the same time he is doing full daily dosage of clear liquid benadryl. now he is on fuciden cream.... and now has hives breaking out on his body - thighs, armpits belly.