People in anaphylactic shock sometimes (often?) need more than one dose, and antihistamine should be taken asap. The epinephrine just bridges the gap until the antihistamine kicks in.
I liked the Ana-kit because the syringe had 2 doses in it (you turned the plunger 90° for the second dose) and the antihistamine. It was much cheaper, and it was pretty easy—- just pull off the needle cap, stick your thigh to the hilt, and press the plunger.
Despite the relative ease of autoinjectors like EpiPen, I was pretty upset when Ana-kit was discontinued and I had to start carrying EpiPens. That’s why I always get the generic 2-pack prescribed and keep it in a ziplock bag with a couple Benadryls.
"To slow absorption of injected antigens (e.g., insect stings), a tourniquet may be placed proximal to the injection site. "
https://www.aafp.org/pubs/afp/issues/2003/1001/p1325.html
The article says that tourniquets are no longer recommended. It doesn't seem like a tourniquet would be of any help if you ingested something but reasonable for insect stings. Anyone who has taken a first aid course gets warned multiple times about the danger of leaving a tourniquet on too long but maybe random people aren't aware of it.