Below the dotted line is my universal solution for hives. I helped 9 people separately suffering from hives after I experienced it myself. Using my technique, all of them have completely gotten rid of chronic urticaria/hives.
None of them however, started with mono or penicillin. So it's the least I can suggest. From my earlier research, drug-induced hives are immediate. If you did not get hives on the day you took the medicine, it probably didn't come from the drugs!!
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i had hives for 1 1/2 year. It took me an insane amount of research, and I finally solved it.
Do the following.... No medicine needed. The cause is "detergent residue" and most people in their life time are not commited enough to solve it. Follow these techniques, it has not failed once.
1.) get rid of all your clothes. Throw them away or put them in a plastic bag air tight. You'll likely never wear them again.
2.) buy all new clothes. Preferably loose instead of tight. If you are budget strapped, buy just enough full sets of clothes for a 2 week rotation only.
3.) buy a new bath towel. Only use this one.
4.) get rid of your bed sheets and blankets. Buy new ones.
5.) before you do laundry, pre rinse 1 cycle with just water.
6.) when you do laundry, don't use any detergent. Use baking soda only. The hard part is making sure the people who share machine with you don't use detergent either!!!!
7.) now wash everything you bought a couple times with baking soda only. Towel, bed sheets, clothes.
8.) only wear your newly purchased clothes, all cotton. No polyester.
9.) only sleep on the bed with the new bed sheets.
10.) exercise daily enough to sweat the existing residue off. If you can't workout and sweat, take a detox bath. Make sure the bath tub is detergent free. No trace of any chemicals etc.
11.) wipe any furniture/couch/chair you might have very clean. Detergent residues are practically invisible.
12.) I have not met one person who was not cleared of this problem after 4-6 weeks. 4 weeks if you are committed!!!!