my 2 year old sun was diaganosed with MRSA and was put on Bactrim Septra and Had a severe reaction to it and now is covered head to toe with a rash, we took him to the ER and they gave him a shot of steriod and benadryl that was 12 hours ago and it hasnt change. If you know anything about this Please let me know. Im just wondering how long the reaction will last. Thank You!!!