I have recently been diagnosis with strep throat and have been taking Pen VK. Last night I started feeling mildly lightheaded, tingling all over my skin, and had a red rash on my chest. I stopped taking my Penicillin and took a Benadryl. I was feeling better but today I am still feeling woozy and had a rash come back. I had a mono test and it came back negative so my MD thinking it was an allergic reaction. How long will I have these symptoms after i stop taking the medication and when does it become concerning? I still have a headache, sore throat, full feeling in my ears, and moderate fatigue.