Me, too, OP! Like many PP, I take over-the-counter antihistamine tablets all mosquito season, but for dabbing on the actual bites I recommend hydrocortisone cream. Here in the UK and in N America and most places I've been you can only buy 1% cream, but last I saw, in France you can get 2% over the counter which is more effective without doubt. Dab on whenever the itching gets out of control again, and if need be cover with a plaster to prevent it wiping off too soon. Maybe ask your GP for a prescription? (yes, I know how hard it is to get a prescription, or indeed a GP appointment, these days)
In Japan I found antihistamine patches, little round clear discs that you could stick on and leave on, worked well. But the ones I've found on Amazon seem less effective than those Japanese ones.
Really for us sufferers it's essential to focus on prevention. DEET is the most reliable repellant I've found, but it is best applied while fully naked because it does damage plastics and that includes plastics in clothing and shoes, and you need a spray to ensure you cover thoroughly and well. I've also found Picardin, sometimes described in UK as PMD, very effective. It's often advertised as natural because it's not DEET, but it's a chemical. I'm not worried by that, I mean water is a chemical, just the contrary, it's a recommendation to me that Picardin is scientifically developed: my point is it's not just some woo-woo botanical like Avon Skin So Soft or citronella that have never worked for me. When holidaying in a mosquito area, I also shower with Incognito soap, but that wouldn't lead me to skip a good strong DEET or Picardin spray, reapplied especially around the ankles at least twice a day. Honestly if I could I'd shower in the stuff in mosquito areas.
p.s. to other PP: the worst mosquitos. Italy is indeed bad, not just Venice but Florence. But the very worst ever I've found were in the Canadian Maritime provinces: New Brunswick, yikes.