The length of time that your allergic response lasts depends on a few factors. The first (and most important factor) is whether or not the reaction you experienced was a classic immune system allergic response. Other reactions to medications can occur that are not technically allergies. The second factor that is important is how long the medication you took stays in your system. Some medications leave your system after a few hours and other stick around for a while. For most allergic reactions, the initial symptoms begin to go away a few hours after the allergen is removed and should be nearly completely gone after 1-2 days. If the itchy rash that you have on your arms and hands is hives
(which would indicate a classic allergic reaction), you should see these go away fairly soon.
It would be nice to know if your reaction was an allergic reaction, and if you are allergic to any other medications. For this reason, I suggest that you schedule an appointment with an allergy specialist. This is the type of doctor
who can test you for an allergy to this medication and other medications. In addition, he or she can provide treatment, should you experience this rash again. Good luck.