About 7 years ago, my husband was prescribed Sulfamethoxazole and...

About 7 years ago, my husband was prescribed Sulfamethoxazole and within days broke out in hives, fever, itching - as sick as he's ever been - worse than what he'd been prescribed the medication for. 2 months ago, our daughter was diagnosed with MRSA and her Dr. prescribed Bactrim - they told us to watch her since her dad had the reaction - 1 week later, she was covered in red spots and needed a prednizone shot - NOW, I'm on MY 3rd day of Sulfamethoxazole and have a terrible itch on my foot and feel itchy all over - don't know if it's just in my head or the beginnings of an allergic reaction :( Could all 3 of us really be allergic?