Also- I recently started a medrol dose pack
That's what I have my money on. Any time you take any prednisolone including methylprednisolone hives can be a side effect.
If you're on a 7 day dose pack and it is the methylprednisolone they should clear up after about a week from discontinuation.
Let us know how things go for you.
^^^ this seems a likely culprit (or the Flonase), given you recently started using it, particularly if your symptoms are relieved w/Benadryl. As Jega said, keep an eye on it (i wouldn't think itd be more than a few days given the pattern you're describing). BUT some points that may be helpful:
Sensitivities can emerge at any time (my daughter has to carry an Epi pen for fruits that she'd eaten for years w/out issue). They often worsen w/repeated exposures; correct me if I misread it, but I'm not seeing this with you? If this isn't happening to you, it could be simple skin irritation.
Hives can also happen for no obvious reason (idiopathic) & as long as they're as mild as your post suggests and ARE NOT IN THE NECK/FACE AREA, they don't normally require urgent attention. If anyone has hives in the face/neck, please stop taking the med & get medical help immediately b/c of the risk of anaphylactic shock.
When you get what you think are hives (vs bug bites), have you noticed swelling and spreading after you scratch the area? This would let you know if its hives vs "no see ums". If you can afford it, given your hx of hives for several years starting with hydrocodone, I'd urge you to get blood work done with an allergist. The panels can identify exactly what substances you're having a reaction to (including fillers in meds).
Im not gonna lie, it cost me over $500 for my kid, but we now know what things she absolutely can't go near without risk of death so for me it was worth it. However, we only ended up going that route after years of idiopathic sporadic outbreaks--just like you, that suddenly got worse.
Think of the fish in finding Nemo with the giants lips & that's what my daughter looked like after two bites of a kiwi. Scary stuff
Allergies can run the gamut from annoying to life threatening & are often hard to figure out, so I also second ^^ please let us know how youre doing k? Feel free to PM me if you want & i hope it's just a case of bug bites!