I have used Advantix few times and I was allways satisfied. I am not sure If you can check allergic reaction….maybe take a drop on your dogs ear or somewhere when you can see the reaction after two days, but I don?t know if rest of pipet could stay few days opened.....
What kind of antiparasitic product did you use in past?
If I were you I would try the Avantix in the morning of a day that you know that you are home to watch for reactions as well as a day when you know a veterinary is open/available. I have not used Advantix on any of my dogs, so I don't know how it works. We have them on Comfortis right now, it is pill they take and withing a few hours the fleas are dead on them and gone for a month. It is fairly new here in the States so I don't know if it available in Italy yet. The other ones that are "safe" is Frontline" and "Advantage", but again I don't know if you have them back in wonderful Italy. (Italy always was my favorite country in Europe, I am from Sweden).
We used Frontline once only and got an allergic reaction from most of the Basenjis and one of the collies - that was several years ago and we've never used it since! I have no experience of the others you mention as I give mine garlic at risky times and they have no troubles with parasites. (We hardly ever have ticks in my part of the Uk). I try to avoid chemicals when I can.