sounds very much like a reaction. did you have anything different that morning, night before? new soap? detergent?

Could be this:
The adverse reactions to drugs are common. Almost any drug can cause an adverse reaction. Reactions range from irritating or mild side effects such as nausea and vomiting to life-threatening anaphylaxis--sp?

A true drug allergy is caused by a series of chemical steps in the body that produce the reaction to a medication.The first time you take the medicine, you may have no problems. However, your body's immune system may produce a substance (antibody) called IgE against that drug. The next time you take the drug, the IgE tells your white blood cells to make a chemical called histamine, which causes your allergy symptoms. A drug allergy may also occur without your body producing IgE. Instead, it might produce other types of antibodies, or have other reactions that do not produce antibodies.

Most drug allergies cause minor skin rashes and hives.

Serum sickness is a delayed type of drug allergy that occus a week or more after you are exposed to a med or vaccines.
~~some technical info from a medplus site

I have heard it said you can become allergic to just about anything - at anytime - no rhyme or reason. It.just.happens.

I wonder if medical pros will downplay meds as the cause, due to reaction not happening within a split second. I mean come on, unless the reaction is in the mouth like as with a peanut allergy, who knows how long it could take?

With all the unknown ingredients in all meds today, it's a wonder anyone can take them.Hope you feel better and get some answers quick.