I Have Identical Twin Daughters. 26. One Now Has A

I have identical twin daughters. 26. One now has a food? allergy. Breathing, swelling and such after eating certain foods. She has pen and keeps Benadryl around. Last blood test said maybe Lupis? HUH. Can testing here sisters blood help. They have torn the same ACL and same shoulder playing Lax. It's a pain, not a family emergency. But all the same before I bring it up I want a general opinion