I was prescribed a 10-day regimen of 500 mg capsules, 3 times/day...

I was prescribed a 10-day regimen of 500 mg capsules, 3 times/day for a tooth infection. First dose at 9:00 pm last night (Friday). Woke up seven hours later with intense itching back of the neck and inner part of both elbows. No other symptoms. Spreading across shoulders and stomach. I'm taking generic antihistamine and applying calamine lotion. No really relieving the symptoms but I'm hoping they will subside my 9:00 am this morning. I'm glad I don't have to try to work in this condition. No plans to take a second dose.