If it might be the spider bite, Benadryl (Or the generic equivalent) should help with swelling and itching- reducing the swelling is often enough to allow improved blood flow so the body can take care of things itself.
Don't ignore danger signals, of course, but benadryl and warm compresses or warm soaks in soapy water (Yay hot baths!) can be very soothing and help things to clear up on their own more quickly.

I'm a beekeeper and I often have to deal with multiple annoying but not life-threatening bites and stings.

Another thing that really helps- If the sting or bite is fresh, meat tenderizer really does help denature the proteins in the venom. A slice of papaya will do the same, but enzyme based meat tenderizer is more concentrated and easier to keep on hand. (Tho the salt in it kinda sucks.)