Red patches all over and swelling in skin looks like allergy patches blood test done nothing found a bit worried itchy feelings aswell regularly?

Red Patches. Hives (medically known as urticaria) appear on the skin as wheals that are red, very itchy, smoothly elevated areas of skin often with a blanched center. They appear in varying shapes and sizes, from a few millimeters to several inches in diameter anywhere on the body. They can be caused by meds, infections, food, and system disease. Treatment is antihistamines and to determine the cause.
Blood tests? You need to consult an allergist if the problem persists over 6 weeks and antihistamine up to 4 doses per day fails to help.
Check it out. May want to consider food allerregies as a cause , as well of considering any changes in diet or environment- laundry detergent, cosmetics, lotions etc..